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	$188.59	3.293%	$194.8003	$194.80	$194.80	$194.80
Purchase #2	$72.83	13.824%	$82.898	$82.90	$82.90	$82.90
Purchase #3	$211.47	7.422%	$227.1653	$227.17	$227.15	$227.20
Purchase #4	$111.68	12.371%	$125.4959	$125.50	$125.50	$125.50
Purchase #5	$93.51	3.557%	$96.8362	$96.84	$96.85	$96.80
Purchase #6	$18.68	11.431%	$20.8153	$20.82	$20.80	$20.80
Purchase #7	$49.54	5.369%	$52.1998	$52.20	$52.20	$52.20
7 purchase totals =	$746.30		$800.2108	$800.23	$800.20	$800.20