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	$145.74	3.238%	$150.4591	$150.46	$150.45	$150.50
Purchase #2	$201.73	4.396%	$210.5981	$210.60	$210.60	$210.60
Purchase #3	$168.96	11.165%	$187.8244	$187.82	$187.80	$187.80
Purchase #4	$14.26	12.637%	$16.062	$16.06	$16.05	$16.10
Purchase #5	$75.83	12.479%	$85.2928	$85.29	$85.30	$85.30
Purchase #6	$87.69	13.317%	$99.3677	$99.37	$99.35	$99.40
Purchase #7	$104.68	5.597%	$110.5389	$110.54	$110.55	$110.50
7 purchase totals =	$798.89		$860.1430	$860.14	$860.10	$860.20