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	$192.59	10.524%	$212.8582	$212.86	$212.85	$212.90
Purchase #2	$134.33	8.323%	$145.5103	$145.51	$145.50	$145.50
Purchase #3	$82.68	3.387%	$85.4804	$85.48	$85.50	$85.50
Purchase #4	$128.69	10.625%	$142.3633	$142.36	$142.35	$142.40
Purchase #5	$195.37	13.230%	$221.2175	$221.22	$221.20	$221.20
Purchase #6	$123.82	7.290%	$132.8465	$132.85	$132.85	$132.80
Purchase #7	$228.67	5.797%	$241.926	$241.93	$241.95	$241.90
7 purchase totals =	$1,086.15		$1,182.2022	$1,182.21	$1,182.20	$1,182.20