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	$200.52	11.443%	$223.4655	$223.47	$223.45	$223.50
Purchase #2	$80.44	8.676%	$87.419	$87.42	$87.40	$87.40
Purchase #3	$77.38	6.393%	$82.3269	$82.33	$82.35	$82.30
Purchase #4	$138.38	10.761%	$153.2711	$153.27	$153.25	$153.30
Purchase #5	$110.86	13.205%	$125.4991	$125.50	$125.50	$125.50
Purchase #6	$226.57	9.598%	$248.3162	$248.32	$248.30	$248.30
Purchase #7	$72.89	11.827%	$81.5107	$81.51	$81.50	$81.50
7 purchase totals =	$907.04		$1,001.8085	$1,001.82	$1,001.75	$1,001.80