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	$198.80	9.830%	$218.342	$218.34	$218.35	$218.30
Purchase #2	$79.86	7.129%	$85.5532	$85.55	$85.55	$85.60
Purchase #3	$155.64	4.404%	$162.4944	$162.49	$162.50	$162.50
Purchase #4	$194.33	8.816%	$211.4621	$211.46	$211.45	$211.50
Purchase #5	$169.30	12.326%	$190.1679	$190.17	$190.15	$190.20
Purchase #6	$59.27	7.777%	$63.8794	$63.88	$63.90	$63.90
Purchase #7	$244.46	7.456%	$262.6869	$262.69	$262.70	$262.70
7 purchase totals =	$1,101.66		$1,194.5859	$1,194.58	$1,194.60	$1,194.70