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	$132.89	10.392%	$146.6999	$146.70	$146.70	$146.70
Purchase #2	$162.38	12.532%	$182.7295	$182.73	$182.75	$182.70
Purchase #3	$28.61	13.717%	$32.5344	$32.53	$32.55	$32.50
Purchase #4	$196.35	13.349%	$222.5608	$222.56	$222.55	$222.60
Purchase #5	$213.34	7.205%	$228.7111	$228.71	$228.70	$228.70
Purchase #6	$218.47	6.710%	$233.1293	$233.13	$233.15	$233.10
Purchase #7	$200.92	3.751%	$208.4565	$208.46	$208.45	$208.50
7 purchase totals =	$1,152.96		$1,254.8215	$1,254.82	$1,254.85	$1,254.80