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	$99.32	7.137%	$106.4085	$106.41	$106.40	$106.40
Purchase #2	$64.82	11.499%	$72.2737	$72.27	$72.25	$72.30
Purchase #3	$213.47	4.753%	$223.6162	$223.62	$223.60	$223.60
Purchase #4	$73.25	8.846%	$79.7297	$79.73	$79.75	$79.70
Purchase #5	$235.75	9.391%	$257.8893	$257.89	$257.90	$257.90
Purchase #6	$181.84	5.460%	$191.7685	$191.77	$191.75	$191.80
Purchase #7	$227.86	5.628%	$240.684	$240.68	$240.70	$240.70
7 purchase totals =	$1,096.31		$1,172.3699	$1,172.37	$1,172.35	$1,172.40