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	$173.32	5.674%	$183.1542	$183.15	$183.15	$183.20
Purchase #2	$188.95	6.111%	$200.4967	$200.50	$200.50	$200.50
Purchase #3	$96.60	8.240%	$104.5598	$104.56	$104.55	$104.60
Purchase #4	$242.73	8.800%	$264.0902	$264.09	$264.10	$264.10
Purchase #5	$42.85	5.565%	$45.2346	$45.23	$45.25	$45.20
Purchase #6	$183.94	8.294%	$199.196	$199.20	$199.20	$199.20
Purchase #7	$69.26	5.148%	$72.8255	$72.83	$72.85	$72.80
7 purchase totals =	$997.65		$1,069.5570	$1,069.56	$1,069.60	$1,069.60