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	$217.85	11.815%	$243.589	$243.59	$243.60	$243.60
Purchase #2	$78.79	4.741%	$82.5254	$82.53	$82.55	$82.50
Purchase #3	$101.94	7.331%	$109.4132	$109.41	$109.40	$109.40
Purchase #4	$11.82	10.316%	$13.0394	$13.04	$13.05	$13.00
Purchase #5	$231.93	9.528%	$254.0283	$254.03	$254.05	$254.00
Purchase #6	$143.27	7.309%	$153.7416	$153.74	$153.75	$153.70
Purchase #7	$78.84	13.465%	$89.4558	$89.46	$89.45	$89.50
7 purchase totals =	$864.44		$945.7927	$945.80	$945.85	$945.70