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	$100.46	5.105%	$105.5885	$105.59	$105.60	$105.60
Purchase #2	$241.27	5.435%	$254.383	$254.38	$254.40	$254.40
Purchase #3	$134.70	10.227%	$148.4758	$148.48	$148.50	$148.50
Purchase #4	$82.26	8.216%	$89.0185	$89.02	$89.00	$89.00
Purchase #5	$17.30	3.634%	$17.9287	$17.93	$17.95	$17.90
Purchase #6	$149.69	10.818%	$165.8835	$165.88	$165.90	$165.90
Purchase #7	$197.57	8.128%	$213.6285	$213.63	$213.65	$213.60
7 purchase totals =	$923.25		$994.9065	$994.91	$995.00	$994.90