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	$61.97	8.858%	$67.4593	$67.46	$67.45	$67.50
Purchase #2	$198.98	10.114%	$219.1048	$219.10	$219.10	$219.10
Purchase #3	$80.28	11.717%	$89.6864	$89.69	$89.70	$89.70
Purchase #4	$89.37	7.811%	$96.3507	$96.35	$96.35	$96.40
Purchase #5	$192.85	4.198%	$200.9458	$200.95	$200.95	$200.90
Purchase #6	$199.50	12.222%	$223.8829	$223.88	$223.90	$223.90
Purchase #7	$10.27	8.226%	$11.1148	$11.11	$11.10	$11.10
7 purchase totals =	$833.22		$908.5447	$908.54	$908.55	$908.60