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	$137.41	13.261%	$155.6319	$155.63	$155.65	$155.60
Purchase #2	$241.42	10.763%	$267.404	$267.40	$267.40	$267.40
Purchase #3	$119.73	6.221%	$127.1784	$127.18	$127.20	$127.20
Purchase #4	$183.93	4.627%	$192.4404	$192.44	$192.45	$192.40
Purchase #5	$191.77	4.357%	$200.1254	$200.13	$200.15	$200.10
Purchase #6	$52.51	5.533%	$55.4154	$55.42	$55.40	$55.40
Purchase #7	$165.38	4.489%	$172.8039	$172.80	$172.80	$172.80
7 purchase totals =	$1,092.15		$1,170.9994	$1,171.00	$1,171.05	$1,170.90