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	$91.39	13.740%	$103.947	$103.95	$103.95	$103.90
Purchase #2	$152.39	13.840%	$173.4808	$173.48	$173.50	$173.50
Purchase #3	$115.80	3.490%	$119.8414	$119.84	$119.85	$119.80
Purchase #4	$150.25	3.202%	$155.061	$155.06	$155.05	$155.10
Purchase #5	$128.38	9.136%	$140.1088	$140.11	$140.10	$140.10
Purchase #6	$17.45	4.848%	$18.296	$18.30	$18.30	$18.30
Purchase #7	$115.33	7.499%	$123.9786	$123.98	$124.00	$124.00
7 purchase totals =	$770.99		$834.7136	$834.72	$834.75	$834.70