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	$62.63	6.146%	$66.4792	$66.48	$66.50	$66.50
Purchase #2	$229.69	11.588%	$256.3065	$256.31	$256.30	$256.30
Purchase #3	$97.57	7.483%	$104.8712	$104.87	$104.85	$104.90
Purchase #4	$250.63	4.220%	$261.2066	$261.21	$261.20	$261.20
Purchase #5	$47.35	9.511%	$51.8535	$51.85	$51.85	$51.90
Purchase #6	$209.98	5.323%	$221.1572	$221.16	$221.15	$221.20
Purchase #7	$138.46	10.404%	$152.8654	$152.87	$152.85	$152.90
7 purchase totals =	$1,036.31		$1,114.7396	$1,114.75	$1,114.70	$1,114.90