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	$106.62	4.169%	$111.065	$111.07	$111.05	$111.10
Purchase #2	$155.32	3.380%	$160.5698	$160.57	$160.55	$160.60
Purchase #3	$200.80	10.494%	$221.872	$221.87	$221.85	$221.90
Purchase #4	$103.34	12.562%	$116.3216	$116.32	$116.30	$116.30
Purchase #5	$70.52	9.221%	$77.0226	$77.02	$77.00	$77.00
Purchase #6	$52.82	5.134%	$55.5318	$55.53	$55.55	$55.50
Purchase #7	$93.97	10.300%	$103.6489	$103.65	$103.65	$103.60
7 purchase totals =	$783.39		$846.0317	$846.03	$845.95	$846.00