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	$33.50	13.753%	$38.1073	$38.11	$38.10	$38.10
Purchase #2	$41.60	10.739%	$46.0674	$46.07	$46.05	$46.10
Purchase #3	$17.73	6.502%	$18.8828	$18.88	$18.90	$18.90
Purchase #4	$101.48	12.674%	$114.3416	$114.34	$114.35	$114.30
Purchase #5	$239.74	12.367%	$269.3886	$269.39	$269.40	$269.40
Purchase #6	$118.42	11.378%	$131.8938	$131.89	$131.90	$131.90
Purchase #7	$28.27	10.115%	$31.1295	$31.13	$31.15	$31.10
7 purchase totals =	$580.74		$649.8110	$649.81	$649.85	$649.80