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	$173.60	10.240%	$191.3766	$191.38	$191.40	$191.40
Purchase #2	$97.32	6.215%	$103.3684	$103.37	$103.35	$103.40
Purchase #3	$81.41	13.563%	$92.4516	$92.45	$92.45	$92.50
Purchase #4	$25.27	4.818%	$26.4875	$26.49	$26.50	$26.50
Purchase #5	$54.76	13.322%	$62.0551	$62.06	$62.05	$62.10
Purchase #6	$155.78	12.621%	$175.441	$175.44	$175.45	$175.40
Purchase #7	$169.41	6.423%	$180.2912	$180.29	$180.30	$180.30
7 purchase totals =	$757.55		$831.4714	$831.48	$831.50	$831.60