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	$139.45	8.833%	$151.7676	$151.77	$151.75	$151.80
Purchase #2	$78.79	13.275%	$89.2494	$89.25	$89.25	$89.20
Purchase #3	$164.45	11.317%	$183.0608	$183.06	$183.05	$183.10
Purchase #4	$229.87	12.627%	$258.8957	$258.90	$258.90	$258.90
Purchase #5	$109.79	9.335%	$120.0389	$120.04	$120.05	$120.00
Purchase #6	$146.41	3.568%	$151.6339	$151.63	$151.65	$151.60
Purchase #7	$120.83	5.713%	$127.733	$127.73	$127.75	$127.70
7 purchase totals =	$989.59		$1,082.3793	$1,082.38	$1,082.40	$1,082.30