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	$194.29	10.849%	$215.3685	$215.37	$215.35	$215.40
Purchase #2	$194.67	12.350%	$218.7117	$218.71	$218.70	$218.70
Purchase #3	$174.52	6.452%	$185.78	$185.78	$185.80	$185.80
Purchase #4	$129.28	13.276%	$146.4432	$146.44	$146.45	$146.40
Purchase #5	$132.71	6.143%	$140.8624	$140.86	$140.85	$140.90
Purchase #6	$54.74	11.343%	$60.9492	$60.95	$60.95	$60.90
Purchase #7	$65.71	9.736%	$72.1075	$72.11	$72.10	$72.10
7 purchase totals =	$945.92		$1,040.2225	$1,040.22	$1,040.20	$1,040.20