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	$187.48	3.745%	$194.5011	$194.50	$194.50	$194.50
Purchase #2	$155.34	10.220%	$171.2157	$171.22	$171.20	$171.20
Purchase #3	$58.51	9.842%	$64.2686	$64.27	$64.25	$64.30
Purchase #4	$16.75	8.327%	$18.1448	$18.14	$18.15	$18.10
Purchase #5	$245.98	4.306%	$256.5719	$256.57	$256.55	$256.60
Purchase #6	$190.28	5.510%	$200.7644	$200.76	$200.75	$200.80
Purchase #7	$247.76	10.745%	$274.3818	$274.38	$274.40	$274.40
7 purchase totals =	$1,102.10		$1,179.8483	$1,179.84	$1,179.80	$1,179.90