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	$200.85	5.187%	$211.2681	$211.27	$211.25	$211.30
Purchase #2	$34.98	7.248%	$37.5154	$37.52	$37.50	$37.50
Purchase #3	$78.52	4.872%	$82.3455	$82.35	$82.35	$82.30
Purchase #4	$218.62	8.120%	$236.3719	$236.37	$236.35	$236.40
Purchase #5	$138.42	12.299%	$155.4443	$155.44	$155.45	$155.40
Purchase #6	$233.56	13.391%	$264.836	$264.84	$264.85	$264.80
Purchase #7	$58.49	13.588%	$66.4376	$66.44	$66.45	$66.40
7 purchase totals =	$963.44		$1,054.2188	$1,054.23	$1,054.20	$1,054.10