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	$189.60	3.494%	$196.2246	$196.22	$196.20	$196.20
Purchase #2	$190.59	8.258%	$206.3289	$206.33	$206.35	$206.30
Purchase #3	$43.80	5.273%	$46.1096	$46.11	$46.10	$46.10
Purchase #4	$160.83	5.623%	$169.8735	$169.87	$169.85	$169.90
Purchase #5	$149.46	11.357%	$166.4342	$166.43	$166.45	$166.40
Purchase #6	$47.78	13.314%	$54.1414	$54.14	$54.15	$54.10
Purchase #7	$91.90	7.831%	$99.0967	$99.10	$99.10	$99.10
7 purchase totals =	$873.96		$938.2089	$938.20	$938.20	$938.10