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	$158.79	13.467%	$180.1742	$180.17	$180.15	$180.20
Purchase #2	$140.44	7.682%	$151.2286	$151.23	$151.25	$151.20
Purchase #3	$92.90	11.862%	$103.9198	$103.92	$103.90	$103.90
Purchase #4	$166.98	11.490%	$186.166	$186.17	$186.15	$186.20
Purchase #5	$235.84	6.416%	$250.9715	$250.97	$250.95	$251.00
Purchase #6	$100.75	4.363%	$105.1457	$105.15	$105.15	$105.10
Purchase #7	$161.89	5.182%	$170.2791	$170.28	$170.30	$170.30
7 purchase totals =	$1,057.59		$1,147.8849	$1,147.89	$1,147.85	$1,147.90