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	$154.54	8.804%	$168.1457	$168.15	$168.15	$168.10
Purchase #2	$89.60	6.541%	$95.4607	$95.46	$95.45	$95.50
Purchase #3	$241.87	7.220%	$259.333	$259.33	$259.35	$259.30
Purchase #4	$69.85	7.311%	$74.9567	$74.96	$74.95	$75.00
Purchase #5	$238.93	6.484%	$254.4222	$254.42	$254.40	$254.40
Purchase #6	$137.54	3.841%	$142.8229	$142.82	$142.80	$142.80
Purchase #7	$64.52	10.680%	$71.4107	$71.41	$71.40	$71.40
7 purchase totals =	$996.85		$1,066.5519	$1,066.55	$1,066.50	$1,066.50