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	$191.31	10.505%	$211.4071	$211.41	$211.40	$211.40
Purchase #2	$172.89	3.865%	$179.5722	$179.57	$179.55	$179.60
Purchase #3	$166.56	4.849%	$174.6365	$174.64	$174.65	$174.60
Purchase #4	$93.67	6.282%	$99.5543	$99.55	$99.55	$99.60
Purchase #5	$18.49	7.763%	$19.9254	$19.93	$19.95	$19.90
Purchase #6	$20.97	7.812%	$22.6082	$22.61	$22.60	$22.60
Purchase #7	$63.84	13.809%	$72.6557	$72.66	$72.65	$72.70
7 purchase totals =	$727.73		$780.3594	$780.37	$780.35	$780.40