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	$200.61	8.749%	$218.1614	$218.16	$218.15	$218.20
Purchase #2	$88.98	8.643%	$96.6705	$96.67	$96.65	$96.70
Purchase #3	$137.27	9.445%	$150.2352	$150.24	$150.25	$150.20
Purchase #4	$37.97	12.394%	$42.676	$42.68	$42.70	$42.70
Purchase #5	$90.59	6.486%	$96.4657	$96.47	$96.45	$96.50
Purchase #6	$76.38	7.683%	$82.2483	$82.25	$82.25	$82.20
Purchase #7	$53.48	3.410%	$55.3037	$55.30	$55.30	$55.30
7 purchase totals =	$685.28		$741.7608	$741.77	$741.75	$741.80