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	$163.49	5.278%	$172.119	$172.12	$172.10	$172.10
Purchase #2	$146.27	9.837%	$160.6586	$160.66	$160.65	$160.70
Purchase #3	$74.78	5.236%	$78.6955	$78.70	$78.70	$78.70
Purchase #4	$190.93	4.478%	$199.4798	$199.48	$199.50	$199.50
Purchase #5	$215.79	10.356%	$238.1372	$238.14	$238.15	$238.10
Purchase #6	$114.77	13.487%	$130.249	$130.25	$130.25	$130.20
Purchase #7	$95.73	5.807%	$101.289	$101.29	$101.30	$101.30
7 purchase totals =	$1,001.76		$1,080.6281	$1,080.64	$1,080.65	$1,080.60