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	$221.72	11.505%	$247.2289	$247.23	$247.25	$247.20
Purchase #2	$28.39	10.829%	$31.4644	$31.46	$31.45	$31.50
Purchase #3	$37.99	13.585%	$43.1509	$43.15	$43.15	$43.20
Purchase #4	$92.44	8.238%	$100.0552	$100.06	$100.05	$100.10
Purchase #5	$104.36	4.604%	$109.1647	$109.16	$109.15	$109.20
Purchase #6	$55.42	5.260%	$58.3351	$58.34	$58.35	$58.30
Purchase #7	$169.88	12.764%	$191.5635	$191.56	$191.55	$191.60
7 purchase totals =	$710.20		$780.9627	$780.96	$780.95	$781.10