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	$160.45	11.681%	$179.1922	$179.19	$179.20	$179.20
Purchase #2	$49.71	8.533%	$53.9518	$53.95	$53.95	$54.00
Purchase #3	$188.65	3.166%	$194.6227	$194.62	$194.60	$194.60
Purchase #4	$242.94	8.551%	$263.7138	$263.71	$263.70	$263.70
Purchase #5	$203.66	4.646%	$213.122	$213.12	$213.10	$213.10
Purchase #6	$89.31	11.652%	$99.7164	$99.72	$99.70	$99.70
Purchase #7	$80.70	11.206%	$89.7432	$89.74	$89.75	$89.70
7 purchase totals =	$1,015.42		$1,094.0621	$1,094.05	$1,094.00	$1,094.00