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	$115.96	12.845%	$130.8551	$130.86	$130.85	$130.90
Purchase #2	$151.84	4.468%	$158.6242	$158.62	$158.60	$158.60
Purchase #3	$40.71	4.261%	$42.4447	$42.44	$42.45	$42.40
Purchase #4	$133.27	6.591%	$142.0538	$142.05	$142.05	$142.10
Purchase #5	$179.95	7.430%	$193.3203	$193.32	$193.30	$193.30
Purchase #6	$233.92	7.414%	$251.2628	$251.26	$251.25	$251.30
Purchase #7	$80.95	6.567%	$86.266	$86.27	$86.25	$86.30
7 purchase totals =	$936.60		$1,004.8269	$1,004.82	$1,004.75	$1,004.90