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	$199.56	5.167%	$209.8713	$209.87	$209.85	$209.90
Purchase #2	$38.86	3.349%	$40.1614	$40.16	$40.15	$40.20
Purchase #3	$16.85	6.144%	$17.8853	$17.89	$17.90	$17.90
Purchase #4	$140.73	7.254%	$150.9386	$150.94	$150.95	$150.90
Purchase #5	$245.76	11.140%	$273.1377	$273.14	$273.15	$273.10
Purchase #6	$159.81	7.503%	$171.8005	$171.80	$171.80	$171.80
Purchase #7	$245.78	3.772%	$255.0508	$255.05	$255.05	$255.10
7 purchase totals =	$1,047.35		$1,118.8456	$1,118.85	$1,118.85	$1,118.90