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	$127.89	3.423%	$132.2677	$132.27	$132.25	$132.30
Purchase #2	$102.60	13.185%	$116.1278	$116.13	$116.15	$116.10
Purchase #3	$242.30	10.447%	$267.6131	$267.61	$267.60	$267.60
Purchase #4	$65.40	10.558%	$72.3049	$72.30	$72.30	$72.30
Purchase #5	$99.95	12.209%	$112.1529	$112.15	$112.15	$112.20
Purchase #6	$225.50	13.638%	$256.2537	$256.25	$256.25	$256.30
Purchase #7	$64.55	8.760%	$70.2046	$70.20	$70.20	$70.20
7 purchase totals =	$928.19		$1,026.9247	$1,026.91	$1,026.90	$1,027.00