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	$9.70	9.259%	$10.5981	$10.60	$10.60	$10.60
Purchase #2	$84.99	5.216%	$89.4231	$89.42	$89.40	$89.40
Purchase #3	$225.91	13.488%	$256.3807	$256.38	$256.40	$256.40
Purchase #4	$57.84	3.397%	$59.8048	$59.80	$59.80	$59.80
Purchase #5	$218.58	4.668%	$228.7833	$228.78	$228.80	$228.80
Purchase #6	$235.98	9.690%	$258.8465	$258.85	$258.85	$258.80
Purchase #7	$118.57	4.666%	$124.1025	$124.10	$124.10	$124.10
7 purchase totals =	$951.57		$1,027.9390	$1,027.93	$1,027.95	$1,027.90