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	$52.91	13.711%	$60.1645	$60.16	$60.15	$60.20
Purchase #2	$84.92	13.595%	$96.4649	$96.46	$96.45	$96.50
Purchase #3	$145.58	3.736%	$151.0189	$151.02	$151.00	$151.00
Purchase #4	$95.25	4.359%	$99.4019	$99.40	$99.40	$99.40
Purchase #5	$181.68	13.758%	$206.6755	$206.68	$206.70	$206.70
Purchase #6	$216.71	13.680%	$246.3559	$246.36	$246.35	$246.40
Purchase #7	$152.91	4.158%	$159.268	$159.27	$159.25	$159.30
7 purchase totals =	$929.96		$1,019.3496	$1,019.35	$1,019.30	$1,019.50