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	$38.70	13.597%	$43.962	$43.96	$43.95	$44.00
Purchase #2	$14.25	7.368%	$15.2999	$15.30	$15.30	$15.30
Purchase #3	$40.57	12.270%	$45.5479	$45.55	$45.55	$45.50
Purchase #4	$31.49	5.560%	$33.2408	$33.24	$33.25	$33.20
Purchase #5	$188.48	3.272%	$194.6471	$194.65	$194.65	$194.60
Purchase #6	$177.48	7.443%	$190.6898	$190.69	$190.70	$190.70
Purchase #7	$83.85	6.422%	$89.2348	$89.23	$89.25	$89.20
7 purchase totals =	$574.82		$612.6223	$612.62	$612.65	$612.50