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	$65.29	9.157%	$71.2686	$71.27	$71.25	$71.30
Purchase #2	$85.53	8.351%	$92.6726	$92.67	$92.65	$92.70
Purchase #3	$216.49	9.754%	$237.6064	$237.61	$237.60	$237.60
Purchase #4	$48.66	4.607%	$50.9018	$50.90	$50.90	$50.90
Purchase #5	$78.49	13.616%	$89.1772	$89.18	$89.20	$89.20
Purchase #6	$28.57	12.104%	$32.0281	$32.03	$32.05	$32.00
Purchase #7	$166.47	5.305%	$175.3012	$175.30	$175.30	$175.30
7 purchase totals =	$689.50		$748.9559	$748.96	$748.95	$749.00