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	$93.96	5.350%	$98.9869	$98.99	$99.00	$99.00
Purchase #2	$18.89	13.848%	$21.5059	$21.51	$21.50	$21.50
Purchase #3	$72.71	8.153%	$78.638	$78.64	$78.65	$78.60
Purchase #4	$30.66	5.215%	$32.2589	$32.26	$32.25	$32.30
Purchase #5	$123.88	10.482%	$136.8651	$136.87	$136.85	$136.90
Purchase #6	$130.97	6.717%	$139.7673	$139.77	$139.75	$139.80
Purchase #7	$146.48	5.163%	$154.0428	$154.04	$154.05	$154.00
7 purchase totals =	$617.55		$662.0649	$662.08	$662.05	$662.10