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	$242.37	4.814%	$254.0377	$254.04	$254.05	$254.00
Purchase #2	$180.47	3.778%	$187.2882	$187.29	$187.30	$187.30
Purchase #3	$74.67	7.840%	$80.5241	$80.52	$80.50	$80.50
Purchase #4	$156.29	7.675%	$168.2853	$168.29	$168.30	$168.30
Purchase #5	$186.51	4.246%	$194.4292	$194.43	$194.45	$194.40
Purchase #6	$80.42	11.617%	$89.7624	$89.76	$89.75	$89.80
Purchase #7	$55.56	3.224%	$57.3513	$57.35	$57.35	$57.40
7 purchase totals =	$976.29		$1,031.6782	$1,031.68	$1,031.70	$1,031.70