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	$64.41	12.159%	$72.2416	$72.24	$72.25	$72.20
Purchase #2	$33.45	8.580%	$36.32	$36.32	$36.30	$36.30
Purchase #3	$36.77	5.701%	$38.8663	$38.87	$38.85	$38.90
Purchase #4	$196.96	6.158%	$209.0888	$209.09	$209.10	$209.10
Purchase #5	$79.91	11.592%	$89.1732	$89.17	$89.15	$89.20
Purchase #6	$112.52	13.344%	$127.5347	$127.53	$127.55	$127.50
Purchase #7	$77.50	10.251%	$85.4445	$85.44	$85.45	$85.40
7 purchase totals =	$601.52		$658.6691	$658.66	$658.65	$658.60