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	$43.60	13.328%	$49.411	$49.41	$49.40	$49.40
Purchase #2	$216.89	3.241%	$223.9194	$223.92	$223.90	$223.90
Purchase #3	$30.89	8.654%	$33.5632	$33.56	$33.55	$33.60
Purchase #4	$86.38	12.559%	$97.2285	$97.23	$97.25	$97.20
Purchase #5	$153.83	5.547%	$162.363	$162.36	$162.35	$162.40
Purchase #6	$79.84	8.612%	$86.7158	$86.72	$86.70	$86.70
Purchase #7	$223.28	12.539%	$251.2771	$251.28	$251.30	$251.30
7 purchase totals =	$834.71		$904.4780	$904.48	$904.45	$904.50