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	$219.35	10.486%	$242.351	$242.35	$242.35	$242.40
Purchase #2	$92.58	13.578%	$105.1505	$105.15	$105.15	$105.20
Purchase #3	$43.27	9.413%	$47.343	$47.34	$47.35	$47.30
Purchase #4	$59.36	11.310%	$66.0736	$66.07	$66.05	$66.10
Purchase #5	$141.50	13.258%	$160.2601	$160.26	$160.25	$160.30
Purchase #6	$226.92	12.544%	$255.3848	$255.38	$255.40	$255.40
Purchase #7	$137.82	9.776%	$151.2933	$151.29	$151.30	$151.30
7 purchase totals =	$920.80		$1,027.8563	$1,027.84	$1,027.85	$1,028.00