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	$197.36	13.114%	$223.2418	$223.24	$223.25	$223.20
Purchase #2	$28.61	12.346%	$32.1422	$32.14	$32.15	$32.10
Purchase #3	$50.80	13.765%	$57.7926	$57.79	$57.80	$57.80
Purchase #4	$82.90	4.706%	$86.8013	$86.80	$86.80	$86.80
Purchase #5	$225.53	12.722%	$254.2219	$254.22	$254.20	$254.20
Purchase #6	$139.25	3.742%	$144.4607	$144.46	$144.45	$144.50
Purchase #7	$212.70	12.770%	$239.8618	$239.86	$239.85	$239.90
7 purchase totals =	$937.15		$1,038.5223	$1,038.51	$1,038.50	$1,038.50