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	$138.62	10.347%	$152.963	$152.96	$152.95	$153.00
Purchase #2	$228.57	9.496%	$250.275	$250.28	$250.30	$250.30
Purchase #3	$6.33	6.800%	$6.7604	$6.76	$6.75	$6.80
Purchase #4	$67.59	7.294%	$72.52	$72.52	$72.50	$72.50
Purchase #5	$100.49	5.151%	$105.6662	$105.67	$105.65	$105.70
Purchase #6	$84.59	4.454%	$88.3576	$88.36	$88.35	$88.40
Purchase #7	$59.32	9.274%	$64.8213	$64.82	$64.80	$64.80
7 purchase totals =	$685.51		$741.3635	$741.37	$741.30	$741.50