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	$64.29	7.784%	$69.2943	$69.29	$69.30	$69.30
Purchase #2	$144.85	4.321%	$151.109	$151.11	$151.10	$151.10
Purchase #3	$199.30	5.296%	$209.8549	$209.85	$209.85	$209.90
Purchase #4	$84.88	12.380%	$95.3881	$95.39	$95.40	$95.40
Purchase #5	$37.99	3.513%	$39.3246	$39.32	$39.30	$39.30
Purchase #6	$122.83	6.240%	$130.4946	$130.49	$130.50	$130.50
Purchase #7	$69.73	12.133%	$78.1903	$78.19	$78.20	$78.20
7 purchase totals =	$723.87		$773.6558	$773.64	$773.65	$773.70