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	$92.28	7.759%	$99.44	$99.44	$99.45	$99.40
Purchase #2	$86.33	4.563%	$90.2692	$90.27	$90.25	$90.30
Purchase #3	$215.42	6.401%	$229.209	$229.21	$229.20	$229.20
Purchase #4	$250.41	3.841%	$260.0282	$260.03	$260.05	$260.00
Purchase #5	$187.70	4.685%	$196.4937	$196.49	$196.50	$196.50
Purchase #6	$164.46	4.236%	$171.4265	$171.43	$171.45	$171.40
Purchase #7	$159.52	9.633%	$174.8866	$174.89	$174.90	$174.90
7 purchase totals =	$1,156.12		$1,221.7532	$1,221.76	$1,221.80	$1,221.70