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	$90.49	8.820%	$98.4712	$98.47	$98.45	$98.50
Purchase #2	$96.95	11.698%	$108.2912	$108.29	$108.30	$108.30
Purchase #3	$189.41	5.821%	$200.4356	$200.44	$200.45	$200.40
Purchase #4	$41.38	6.459%	$44.0527	$44.05	$44.05	$44.10
Purchase #5	$48.56	11.407%	$54.0992	$54.10	$54.10	$54.10
Purchase #6	$145.34	7.770%	$156.6329	$156.63	$156.65	$156.60
Purchase #7	$12.34	11.131%	$13.7136	$13.71	$13.70	$13.70
7 purchase totals =	$624.47		$675.6964	$675.69	$675.70	$675.70