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	$197.50	5.671%	$208.7002	$208.70	$208.70	$208.70
Purchase #2	$158.28	4.473%	$165.3599	$165.36	$165.35	$165.40
Purchase #3	$45.54	4.136%	$47.4235	$47.42	$47.40	$47.40
Purchase #4	$90.87	13.760%	$103.3737	$103.37	$103.35	$103.40
Purchase #5	$91.50	10.556%	$101.1587	$101.16	$101.15	$101.20
Purchase #6	$56.72	9.375%	$62.0375	$62.04	$62.05	$62.00
Purchase #7	$55.90	13.361%	$63.3688	$63.37	$63.35	$63.40
7 purchase totals =	$696.31		$751.4223	$751.42	$751.35	$751.50