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	$97.67	3.506%	$101.0943	$101.09	$101.10	$101.10
Purchase #2	$76.45	13.105%	$86.4688	$86.47	$86.45	$86.50
Purchase #3	$25.39	8.361%	$27.5129	$27.51	$27.50	$27.50
Purchase #4	$116.56	13.654%	$132.4751	$132.48	$132.50	$132.50
Purchase #5	$72.95	3.280%	$75.3428	$75.34	$75.35	$75.30
Purchase #6	$7.28	7.829%	$7.85	$7.85	$7.85	$7.90
Purchase #7	$240.55	6.551%	$256.3084	$256.31	$256.30	$256.30
7 purchase totals =	$636.85		$687.0523	$687.05	$687.05	$687.10