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	$185.36	13.835%	$211.0046	$211.00	$211.00	$211.00
Purchase #2	$89.52	3.777%	$92.9012	$92.90	$92.90	$92.90
Purchase #3	$27.35	3.562%	$28.3242	$28.32	$28.30	$28.30
Purchase #4	$103.92	7.679%	$111.9	$111.90	$111.90	$111.90
Purchase #5	$89.54	11.159%	$99.5318	$99.53	$99.55	$99.50
Purchase #6	$57.89	10.502%	$63.9696	$63.97	$63.95	$64.00
Purchase #7	$133.77	9.209%	$146.0889	$146.09	$146.10	$146.10
7 purchase totals =	$687.35		$753.7203	$753.71	$753.70	$753.70