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	$176.37	5.353%	$185.8111	$185.81	$185.80	$185.80
Purchase #2	$246.40	10.498%	$272.2671	$272.27	$272.25	$272.30
Purchase #3	$137.83	6.144%	$146.2983	$146.30	$146.30	$146.30
Purchase #4	$223.78	12.654%	$252.0971	$252.10	$252.10	$252.10
Purchase #5	$89.95	8.665%	$97.7442	$97.74	$97.75	$97.70
Purchase #6	$7.61	12.428%	$8.5558	$8.56	$8.55	$8.60
Purchase #7	$117.76	4.781%	$123.3901	$123.39	$123.40	$123.40
7 purchase totals =	$999.70		$1,086.1637	$1,086.17	$1,086.15	$1,086.20