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	$64.74	11.842%	$72.4065	$72.41	$72.40	$72.40
Purchase #2	$91.54	8.718%	$99.5205	$99.52	$99.50	$99.50
Purchase #3	$101.58	6.809%	$108.4966	$108.50	$108.50	$108.50
Purchase #4	$126.80	5.105%	$133.2731	$133.27	$133.25	$133.30
Purchase #5	$153.77	9.689%	$168.6688	$168.67	$168.65	$168.70
Purchase #6	$77.99	11.393%	$86.8754	$86.88	$86.90	$86.90
Purchase #7	$25.29	12.123%	$28.3559	$28.36	$28.35	$28.40
7 purchase totals =	$641.71		$697.5968	$697.61	$697.55	$697.70