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	$69.98	3.123%	$72.1655	$72.17	$72.15	$72.20
Purchase #2	$40.29	12.515%	$45.3323	$45.33	$45.35	$45.30
Purchase #3	$77.58	10.648%	$85.8407	$85.84	$85.85	$85.80
Purchase #4	$234.69	4.651%	$245.6054	$245.61	$245.60	$245.60
Purchase #5	$103.72	10.410%	$114.5173	$114.52	$114.50	$114.50
Purchase #6	$114.86	6.274%	$122.0663	$122.07	$122.05	$122.10
Purchase #7	$95.88	4.521%	$100.2147	$100.21	$100.20	$100.20
7 purchase totals =	$737.00		$785.7422	$785.75	$785.70	$785.70