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	$23.34	11.180%	$25.9494	$25.95	$25.95	$25.90
Purchase #2	$24.31	6.315%	$25.8452	$25.85	$25.85	$25.80
Purchase #3	$37.98	10.594%	$42.0036	$42.00	$42.00	$42.00
Purchase #4	$211.69	6.311%	$225.0498	$225.05	$225.05	$225.00
Purchase #5	$70.70	11.618%	$78.9139	$78.91	$78.90	$78.90
Purchase #6	$41.57	12.725%	$46.8598	$46.86	$46.85	$46.90
Purchase #7	$79.67	12.615%	$89.7204	$89.72	$89.70	$89.70
7 purchase totals =	$489.26		$534.3421	$534.34	$534.30	$534.20