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	$92.46	11.754%	$103.3277	$103.33	$103.35	$103.30
Purchase #2	$192.52	8.587%	$209.0517	$209.05	$209.05	$209.10
Purchase #3	$188.26	4.191%	$196.15	$196.15	$196.15	$196.20
Purchase #4	$48.62	6.377%	$51.7205	$51.72	$51.70	$51.70
Purchase #5	$67.55	4.589%	$70.6499	$70.65	$70.65	$70.60
Purchase #6	$94.94	12.499%	$106.8066	$106.81	$106.80	$106.80
Purchase #7	$156.47	9.523%	$171.3706	$171.37	$171.35	$171.40
7 purchase totals =	$840.82		$909.0770	$909.08	$909.05	$909.10