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	$210.48	10.778%	$233.1655	$233.17	$233.15	$233.20
Purchase #2	$74.34	3.163%	$76.6914	$76.69	$76.70	$76.70
Purchase #3	$152.84	9.183%	$166.8753	$166.88	$166.90	$166.90
Purchase #4	$152.68	12.344%	$171.5268	$171.53	$171.55	$171.50
Purchase #5	$56.71	5.498%	$59.8279	$59.83	$59.85	$59.80
Purchase #6	$49.86	3.734%	$51.7218	$51.72	$51.70	$51.70
Purchase #7	$55.82	13.404%	$63.3021	$63.30	$63.30	$63.30
7 purchase totals =	$752.73		$823.1108	$823.12	$823.15	$823.10