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	$180.54	10.732%	$199.9156	$199.92	$199.90	$199.90
Purchase #2	$83.44	7.181%	$89.4318	$89.43	$89.45	$89.40
Purchase #3	$210.95	5.141%	$221.7949	$221.79	$221.80	$221.80
Purchase #4	$204.70	3.147%	$211.1419	$211.14	$211.15	$211.10
Purchase #5	$52.72	11.680%	$58.8777	$58.88	$58.90	$58.90
Purchase #6	$137.37	10.737%	$152.1194	$152.12	$152.10	$152.10
Purchase #7	$24.82	13.153%	$28.0846	$28.08	$28.10	$28.10
7 purchase totals =	$894.54		$961.3659	$961.36	$961.40	$961.30