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	$185.33	8.204%	$200.5345	$200.53	$200.55	$200.50
Purchase #2	$47.68	7.503%	$51.2574	$51.26	$51.25	$51.30
Purchase #3	$226.87	10.319%	$250.2807	$250.28	$250.30	$250.30
Purchase #4	$210.36	12.742%	$237.1641	$237.16	$237.15	$237.20
Purchase #5	$177.70	4.515%	$185.7232	$185.72	$185.70	$185.70
Purchase #6	$38.96	5.824%	$41.229	$41.23	$41.25	$41.20
Purchase #7	$122.61	13.451%	$139.1023	$139.10	$139.10	$139.10
7 purchase totals =	$1,009.51		$1,105.2912	$1,105.28	$1,105.30	$1,105.30