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	$221.44	5.411%	$233.4221	$233.42	$233.40	$233.40
Purchase #2	$213.96	6.716%	$228.3296	$228.33	$228.35	$228.30
Purchase #3	$128.96	8.511%	$139.9358	$139.94	$139.95	$139.90
Purchase #4	$178.99	9.118%	$195.3103	$195.31	$195.30	$195.30
Purchase #5	$60.57	9.229%	$66.16	$66.16	$66.15	$66.20
Purchase #6	$98.41	13.205%	$111.405	$111.41	$111.40	$111.40
Purchase #7	$235.43	6.427%	$250.5611	$250.56	$250.55	$250.60
7 purchase totals =	$1,137.76		$1,225.1239	$1,225.13	$1,225.10	$1,225.10