Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$201.66	12.563%	$226.9945	$226.99	$227.00	$227.00
Purchase #2	$159.84	12.494%	$179.8104	$179.81	$179.80	$179.80
Purchase #3	$164.50	4.279%	$171.539	$171.54	$171.55	$171.50
Purchase #4	$187.80	4.771%	$196.7599	$196.76	$196.75	$196.80
Purchase #5	$99.78	13.316%	$113.0667	$113.07	$113.05	$113.10
Purchase #6	$122.64	12.152%	$137.5432	$137.54	$137.55	$137.50
Purchase #7	$130.67	13.284%	$148.0282	$148.03	$148.05	$148.00
7 purchase totals =	$1,066.89		$1,173.7419	$1,173.74	$1,173.75	$1,173.70