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	$107.39	5.727%	$113.5402	$113.54	$113.55	$113.50
Purchase #2	$222.28	5.528%	$234.5676	$234.57	$234.55	$234.60
Purchase #3	$225.58	3.784%	$234.1159	$234.12	$234.10	$234.10
Purchase #4	$158.33	13.239%	$179.2913	$179.29	$179.30	$179.30
Purchase #5	$51.95	7.539%	$55.8665	$55.87	$55.85	$55.90
Purchase #6	$82.98	6.793%	$88.6168	$88.62	$88.60	$88.60
Purchase #7	$222.34	8.109%	$240.3696	$240.37	$240.35	$240.40
7 purchase totals =	$1,070.85		$1,146.3679	$1,146.38	$1,146.30	$1,146.40