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	$30.48	12.107%	$34.1702	$34.17	$34.15	$34.20
Purchase #2	$96.84	4.144%	$100.853	$100.85	$100.85	$100.90
Purchase #3	$209.48	9.731%	$229.8645	$229.86	$229.85	$229.90
Purchase #4	$171.53	4.443%	$179.1511	$179.15	$179.15	$179.20
Purchase #5	$9.89	7.363%	$10.6182	$10.62	$10.60	$10.60
Purchase #6	$224.27	8.275%	$242.8283	$242.83	$242.85	$242.80
Purchase #7	$232.67	7.690%	$250.5623	$250.56	$250.55	$250.60
7 purchase totals =	$975.16		$1,048.0476	$1,048.04	$1,048.00	$1,048.20