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	$87.64	8.147%	$94.78	$94.78	$94.80	$94.80
Purchase #2	$189.41	13.512%	$215.0031	$215.00	$215.00	$215.00
Purchase #3	$91.47	3.359%	$94.5425	$94.54	$94.55	$94.50
Purchase #4	$170.75	10.821%	$189.2269	$189.23	$189.25	$189.20
Purchase #5	$181.26	8.402%	$196.4895	$196.49	$196.50	$196.50
Purchase #6	$67.46	13.323%	$76.4477	$76.45	$76.45	$76.40
Purchase #7	$187.94	11.476%	$209.508	$209.51	$209.50	$209.50
7 purchase totals =	$975.93		$1,075.9977	$1,076.00	$1,076.05	$1,075.90