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	$238.46	12.551%	$268.3891	$268.39	$268.40	$268.40
Purchase #2	$235.75	5.217%	$248.0491	$248.05	$248.05	$248.00
Purchase #3	$110.87	11.351%	$123.4549	$123.45	$123.45	$123.50
Purchase #4	$37.75	13.546%	$42.8636	$42.86	$42.85	$42.90
Purchase #5	$222.69	11.134%	$247.4843	$247.48	$247.50	$247.50
Purchase #6	$25.81	6.243%	$27.4213	$27.42	$27.40	$27.40
Purchase #7	$179.30	6.495%	$190.9455	$190.95	$190.95	$190.90
7 purchase totals =	$1,050.63		$1,148.6078	$1,148.60	$1,148.60	$1,148.60