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	$219.88	12.202%	$246.7098	$246.71	$246.70	$246.70
Purchase #2	$99.63	12.686%	$112.2691	$112.27	$112.25	$112.30
Purchase #3	$136.54	12.819%	$154.0431	$154.04	$154.05	$154.00
Purchase #4	$185.99	12.118%	$208.5283	$208.53	$208.55	$208.50
Purchase #5	$53.96	10.143%	$59.4332	$59.43	$59.45	$59.40
Purchase #6	$105.77	9.658%	$115.9853	$115.99	$116.00	$116.00
Purchase #7	$111.87	10.253%	$123.34	$123.34	$123.35	$123.30
7 purchase totals =	$913.64		$1,020.3088	$1,020.31	$1,020.35	$1,020.20