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	$219.68	8.734%	$238.8669	$238.87	$238.85	$238.90
Purchase #2	$88.72	3.341%	$91.6841	$91.68	$91.70	$91.70
Purchase #3	$28.61	10.189%	$31.5251	$31.53	$31.55	$31.50
Purchase #4	$94.61	4.366%	$98.7407	$98.74	$98.75	$98.70
Purchase #5	$64.89	11.796%	$72.5444	$72.54	$72.55	$72.50
Purchase #6	$55.36	10.521%	$61.1844	$61.18	$61.20	$61.20
Purchase #7	$102.72	4.827%	$107.6783	$107.68	$107.70	$107.70
7 purchase totals =	$654.59		$702.2239	$702.22	$702.30	$702.20