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	$40.60	11.572%	$45.2982	$45.30	$45.30	$45.30
Purchase #2	$16.41	13.219%	$18.5792	$18.58	$18.60	$18.60
Purchase #3	$158.72	4.801%	$166.3401	$166.34	$166.35	$166.30
Purchase #4	$233.88	9.512%	$256.1267	$256.13	$256.15	$256.10
Purchase #5	$91.56	6.165%	$97.2047	$97.20	$97.20	$97.20
Purchase #6	$31.77	5.150%	$33.4062	$33.41	$33.40	$33.40
Purchase #7	$90.57	8.734%	$98.4804	$98.48	$98.50	$98.50
7 purchase totals =	$663.51		$715.4355	$715.44	$715.50	$715.40