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	$210.47	3.845%	$218.5626	$218.56	$218.55	$218.60
Purchase #2	$169.45	12.459%	$190.5618	$190.56	$190.55	$190.60
Purchase #3	$72.39	9.143%	$79.0086	$79.01	$79.00	$79.00
Purchase #4	$180.68	7.316%	$193.8985	$193.90	$193.90	$193.90
Purchase #5	$172.36	11.165%	$191.604	$191.60	$191.60	$191.60
Purchase #6	$118.82	10.658%	$131.4838	$131.48	$131.50	$131.50
Purchase #7	$170.39	12.300%	$191.348	$191.35	$191.35	$191.30
7 purchase totals =	$1,094.56		$1,196.4673	$1,196.46	$1,196.45	$1,196.50