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	$231.86	5.715%	$245.1108	$245.11	$245.10	$245.10
Purchase #2	$50.83	10.754%	$56.2963	$56.30	$56.30	$56.30
Purchase #3	$201.48	11.626%	$224.9041	$224.90	$224.90	$224.90
Purchase #4	$222.54	4.223%	$231.9379	$231.94	$231.95	$231.90
Purchase #5	$172.56	10.211%	$190.1801	$190.18	$190.20	$190.20
Purchase #6	$25.33	6.331%	$26.9336	$26.93	$26.95	$26.90
Purchase #7	$78.79	9.704%	$86.4358	$86.44	$86.45	$86.40
7 purchase totals =	$983.39		$1,061.7986	$1,061.80	$1,061.85	$1,061.70