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	$40.93	10.588%	$45.2637	$45.26	$45.25	$45.30
Purchase #2	$20.91	11.192%	$23.2502	$23.25	$23.25	$23.30
Purchase #3	$45.63	11.444%	$50.8519	$50.85	$50.85	$50.90
Purchase #4	$35.80	4.622%	$37.4547	$37.45	$37.45	$37.50
Purchase #5	$165.71	6.346%	$176.226	$176.23	$176.25	$176.20
Purchase #6	$146.91	3.710%	$152.3604	$152.36	$152.35	$152.40
Purchase #7	$42.94	10.124%	$47.2872	$47.29	$47.30	$47.30
7 purchase totals =	$498.83		$532.6941	$532.69	$532.70	$532.90