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	$64.57	5.204%	$67.9302	$67.93	$67.95	$67.90
Purchase #2	$48.36	7.850%	$52.1563	$52.16	$52.15	$52.20
Purchase #3	$80.30	6.847%	$85.7981	$85.80	$85.80	$85.80
Purchase #4	$162.52	4.305%	$169.5165	$169.52	$169.50	$169.50
Purchase #5	$88.40	3.378%	$91.3862	$91.39	$91.40	$91.40
Purchase #6	$224.73	13.147%	$254.2753	$254.28	$254.30	$254.30
Purchase #7	$79.94	10.167%	$88.0675	$88.07	$88.05	$88.10
7 purchase totals =	$748.82		$809.1301	$809.15	$809.15	$809.20