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	$226.56	3.401%	$234.2653	$234.27	$234.25	$234.30
Purchase #2	$243.53	8.769%	$264.8851	$264.89	$264.90	$264.90
Purchase #3	$104.78	11.412%	$116.7375	$116.74	$116.75	$116.70
Purchase #4	$224.77	5.402%	$236.9121	$236.91	$236.90	$236.90
Purchase #5	$175.57	5.861%	$185.8602	$185.86	$185.85	$185.90
Purchase #6	$69.34	4.766%	$72.6447	$72.64	$72.65	$72.60
Purchase #7	$197.96	3.324%	$204.5402	$204.54	$204.55	$204.50
7 purchase totals =	$1,242.51		$1,315.8451	$1,315.85	$1,315.85	$1,315.80