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	$188.95	13.753%	$214.9363	$214.94	$214.95	$214.90
Purchase #2	$85.44	6.136%	$90.6826	$90.68	$90.70	$90.70
Purchase #3	$198.91	8.165%	$215.151	$215.15	$215.15	$215.20
Purchase #4	$154.53	3.121%	$159.3529	$159.35	$159.35	$159.40
Purchase #5	$97.41	12.309%	$109.4002	$109.40	$109.40	$109.40
Purchase #6	$166.32	9.513%	$182.142	$182.14	$182.15	$182.10
Purchase #7	$54.53	9.779%	$59.8625	$59.86	$59.85	$59.90
7 purchase totals =	$946.09		$1,031.5275	$1,031.52	$1,031.55	$1,031.60