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	$165.78	7.656%	$178.4721	$178.47	$178.45	$178.50
Purchase #2	$190.90	9.761%	$209.5337	$209.53	$209.55	$209.50
Purchase #3	$78.95	5.786%	$83.518	$83.52	$83.50	$83.50
Purchase #4	$193.85	10.690%	$214.5726	$214.57	$214.55	$214.60
Purchase #5	$91.52	10.705%	$101.3172	$101.32	$101.30	$101.30
Purchase #6	$90.29	10.570%	$99.8337	$99.83	$99.85	$99.80
Purchase #7	$227.27	8.555%	$246.7129	$246.71	$246.70	$246.70
7 purchase totals =	$1,038.56		$1,133.9602	$1,133.95	$1,133.90	$1,133.90