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	$81.28	10.165%	$89.5421	$89.54	$89.55	$89.50
Purchase #2	$185.31	5.620%	$195.7244	$195.72	$195.70	$195.70
Purchase #3	$181.36	11.441%	$202.1094	$202.11	$202.10	$202.10
Purchase #4	$70.61	8.478%	$76.5963	$76.60	$76.60	$76.60
Purchase #5	$54.66	9.353%	$59.7723	$59.77	$59.75	$59.80
Purchase #6	$178.95	11.609%	$199.7243	$199.72	$199.70	$199.70
Purchase #7	$180.61	10.502%	$199.5777	$199.58	$199.60	$199.60
7 purchase totals =	$932.78		$1,023.0465	$1,023.04	$1,023.00	$1,023.00