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	$189.26	4.707%	$198.1685	$198.17	$198.15	$198.20
Purchase #2	$73.52	13.596%	$83.5158	$83.52	$83.50	$83.50
Purchase #3	$245.96	4.190%	$256.2657	$256.27	$256.25	$256.30
Purchase #4	$250.52	5.428%	$264.1182	$264.12	$264.10	$264.10
Purchase #5	$153.83	7.199%	$164.9042	$164.90	$164.90	$164.90
Purchase #6	$128.74	6.495%	$137.1017	$137.10	$137.10	$137.10
Purchase #7	$19.30	13.474%	$21.9005	$21.90	$21.90	$21.90
7 purchase totals =	$1,061.13		$1,125.9746	$1,125.98	$1,125.90	$1,126.00