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	$182.57	8.616%	$198.3002	$198.30	$198.30	$198.30
Purchase #2	$95.71	5.422%	$100.8994	$100.90	$100.90	$100.90
Purchase #3	$195.45	8.197%	$211.471	$211.47	$211.45	$211.50
Purchase #4	$166.50	8.634%	$180.8756	$180.88	$180.90	$180.90
Purchase #5	$112.86	9.111%	$123.1427	$123.14	$123.15	$123.10
Purchase #6	$135.83	3.701%	$140.8571	$140.86	$140.85	$140.90
Purchase #7	$210.59	6.429%	$224.1288	$224.13	$224.15	$224.10
7 purchase totals =	$1,099.51		$1,179.6748	$1,179.68	$1,179.70	$1,179.70