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	$168.79	13.182%	$191.0399	$191.04	$191.05	$191.00
Purchase #2	$39.57	3.181%	$40.8287	$40.83	$40.85	$40.80
Purchase #3	$19.75	5.135%	$20.7642	$20.76	$20.75	$20.80
Purchase #4	$53.44	3.349%	$55.2297	$55.23	$55.25	$55.20
Purchase #5	$42.43	8.596%	$46.0773	$46.08	$46.10	$46.10
Purchase #6	$136.71	7.599%	$147.0986	$147.10	$147.10	$147.10
Purchase #7	$173.62	9.723%	$190.5011	$190.50	$190.50	$190.50
7 purchase totals =	$634.31		$691.5395	$691.54	$691.60	$691.50