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	$208.91	9.643%	$229.0552	$229.06	$229.05	$229.10
Purchase #2	$55.81	4.253%	$58.1836	$58.18	$58.20	$58.20
Purchase #3	$31.84	4.155%	$33.163	$33.16	$33.15	$33.20
Purchase #4	$124.75	10.264%	$137.5543	$137.55	$137.55	$137.60
Purchase #5	$159.87	5.625%	$168.8627	$168.86	$168.85	$168.90
Purchase #6	$196.90	12.782%	$222.0678	$222.07	$222.05	$222.10
Purchase #7	$138.47	13.360%	$156.9696	$156.97	$156.95	$157.00
7 purchase totals =	$916.55		$1,005.8562	$1,005.85	$1,005.80	$1,006.10