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	$57.77	3.330%	$59.6937	$59.69	$59.70	$59.70
Purchase #2	$191.34	5.316%	$201.5116	$201.51	$201.50	$201.50
Purchase #3	$44.71	4.369%	$46.6634	$46.66	$46.65	$46.70
Purchase #4	$23.75	3.596%	$24.6041	$24.60	$24.60	$24.60
Purchase #5	$182.45	7.515%	$196.1611	$196.16	$196.15	$196.20
Purchase #6	$221.33	5.401%	$233.284	$233.28	$233.30	$233.30
Purchase #7	$141.50	13.186%	$160.1582	$160.16	$160.15	$160.20
7 purchase totals =	$862.85		$922.0761	$922.06	$922.05	$922.20