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	$160.64	8.584%	$174.4293	$174.43	$174.45	$174.40
Purchase #2	$154.78	4.770%	$162.163	$162.16	$162.15	$162.20
Purchase #3	$42.90	8.251%	$46.4397	$46.44	$46.45	$46.40
Purchase #4	$67.67	6.143%	$71.827	$71.83	$71.85	$71.80
Purchase #5	$202.95	12.398%	$228.1117	$228.11	$228.10	$228.10
Purchase #6	$74.93	9.561%	$82.0941	$82.09	$82.10	$82.10
Purchase #7	$130.68	13.616%	$148.4734	$148.47	$148.45	$148.50
7 purchase totals =	$834.55		$913.5382	$913.53	$913.55	$913.50