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	$99.67	4.613%	$104.2678	$104.27	$104.25	$104.30
Purchase #2	$119.76	9.196%	$130.7731	$130.77	$130.75	$130.80
Purchase #3	$24.46	5.719%	$25.8589	$25.86	$25.85	$25.90
Purchase #4	$193.32	5.607%	$204.1595	$204.16	$204.15	$204.20
Purchase #5	$245.48	5.608%	$259.2465	$259.25	$259.25	$259.20
Purchase #6	$91.70	9.512%	$100.4225	$100.42	$100.40	$100.40
Purchase #7	$229.27	6.296%	$243.7048	$243.70	$243.70	$243.70
7 purchase totals =	$1,003.66		$1,068.4331	$1,068.43	$1,068.35	$1,068.50