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	$41.69	5.378%	$43.9321	$43.93	$43.95	$43.90
Purchase #2	$205.70	11.707%	$229.7813	$229.78	$229.80	$229.80
Purchase #3	$50.94	6.691%	$54.3484	$54.35	$54.35	$54.30
Purchase #4	$89.38	8.476%	$96.9558	$96.96	$96.95	$97.00
Purchase #5	$231.30	6.399%	$246.1009	$246.10	$246.10	$246.10
Purchase #6	$194.31	7.643%	$209.1611	$209.16	$209.15	$209.20
Purchase #7	$243.89	3.170%	$251.6213	$251.62	$251.60	$251.60
7 purchase totals =	$1,057.21		$1,131.9009	$1,131.90	$1,131.90	$1,131.90