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	$202.35	6.867%	$216.2454	$216.25	$216.25	$216.20
Purchase #2	$140.89	9.152%	$153.7843	$153.78	$153.80	$153.80
Purchase #3	$224.85	12.758%	$253.5364	$253.54	$253.55	$253.50
Purchase #4	$41.91	3.771%	$43.4904	$43.49	$43.50	$43.50
Purchase #5	$235.74	12.174%	$264.439	$264.44	$264.45	$264.40
Purchase #6	$234.41	9.541%	$256.7751	$256.78	$256.80	$256.80
Purchase #7	$189.41	4.568%	$198.0622	$198.06	$198.05	$198.10
7 purchase totals =	$1,269.56		$1,386.3328	$1,386.34	$1,386.40	$1,386.30