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	$216.40	12.535%	$243.5257	$243.53	$243.55	$243.50
Purchase #2	$228.74	9.710%	$250.9507	$250.95	$250.95	$251.00
Purchase #3	$137.78	9.184%	$150.4337	$150.43	$150.45	$150.40
Purchase #4	$55.42	5.153%	$58.2758	$58.28	$58.30	$58.30
Purchase #5	$91.40	10.684%	$101.1652	$101.17	$101.15	$101.20
Purchase #6	$67.54	7.447%	$72.5697	$72.57	$72.55	$72.60
Purchase #7	$232.50	7.769%	$250.5629	$250.56	$250.55	$250.60
7 purchase totals =	$1,029.78		$1,127.4837	$1,127.49	$1,127.50	$1,127.60