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	$119.67	6.310%	$127.2212	$127.22	$127.20	$127.20
Purchase #2	$125.94	3.616%	$130.494	$130.49	$130.50	$130.50
Purchase #3	$85.36	7.165%	$91.476	$91.48	$91.50	$91.50
Purchase #4	$170.59	10.722%	$188.8807	$188.88	$188.90	$188.90
Purchase #5	$130.32	6.676%	$139.0202	$139.02	$139.00	$139.00
Purchase #6	$188.74	7.565%	$203.0182	$203.02	$203.00	$203.00
Purchase #7	$172.86	7.363%	$185.5877	$185.59	$185.60	$185.60
7 purchase totals =	$993.48		$1,065.6980	$1,065.70	$1,065.70	$1,065.70