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	$199.98	9.366%	$218.7101	$218.71	$218.70	$218.70
Purchase #2	$34.51	11.149%	$38.3575	$38.36	$38.35	$38.40
Purchase #3	$175.93	5.181%	$185.0449	$185.04	$185.05	$185.00
Purchase #4	$110.51	4.650%	$115.6487	$115.65	$115.65	$115.60
Purchase #5	$89.90	9.779%	$98.6913	$98.69	$98.70	$98.70
Purchase #6	$158.52	13.749%	$180.3149	$180.31	$180.30	$180.30
Purchase #7	$199.46	5.200%	$209.8319	$209.83	$209.85	$209.80
7 purchase totals =	$968.81		$1,046.5993	$1,046.59	$1,046.60	$1,046.50