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	$196.56	7.836%	$211.9624	$211.96	$211.95	$212.00
Purchase #2	$115.25	3.815%	$119.6468	$119.65	$119.65	$119.60
Purchase #3	$93.98	9.747%	$103.1402	$103.14	$103.15	$103.10
Purchase #4	$123.49	11.406%	$137.5753	$137.58	$137.60	$137.60
Purchase #5	$52.50	4.498%	$54.8615	$54.86	$54.85	$54.90
Purchase #6	$50.46	7.423%	$54.2056	$54.21	$54.20	$54.20
Purchase #7	$26.39	9.200%	$28.8179	$28.82	$28.80	$28.80
7 purchase totals =	$658.63		$710.2097	$710.22	$710.20	$710.20