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	$190.40	12.264%	$213.7507	$213.75	$213.75	$213.80
Purchase #2	$239.64	10.816%	$265.5595	$265.56	$265.55	$265.60
Purchase #3	$58.88	13.795%	$67.0025	$67.00	$67.00	$67.00
Purchase #4	$224.60	4.339%	$234.3454	$234.35	$234.35	$234.30
Purchase #5	$41.83	3.821%	$43.4283	$43.43	$43.45	$43.40
Purchase #6	$36.84	6.251%	$39.1429	$39.14	$39.15	$39.10
Purchase #7	$147.95	3.172%	$152.643	$152.64	$152.65	$152.60
7 purchase totals =	$940.14		$1,015.8723	$1,015.87	$1,015.90	$1,015.80