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	$46.41	3.807%	$48.1768	$48.18	$48.20	$48.20
Purchase #2	$79.70	11.123%	$88.565	$88.57	$88.55	$88.60
Purchase #3	$69.72	13.136%	$78.8784	$78.88	$78.90	$78.90
Purchase #4	$93.70	10.662%	$103.6903	$103.69	$103.70	$103.70
Purchase #5	$57.87	9.141%	$63.1599	$63.16	$63.15	$63.20
Purchase #6	$239.80	4.445%	$250.4591	$250.46	$250.45	$250.50
Purchase #7	$238.77	7.425%	$256.4987	$256.50	$256.50	$256.50
7 purchase totals =	$825.97		$889.4282	$889.44	$889.45	$889.60