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	$131.89	10.388%	$145.5907	$145.59	$145.60	$145.60
Purchase #2	$213.67	4.397%	$223.0651	$223.07	$223.05	$223.10
Purchase #3	$141.68	9.385%	$154.9767	$154.98	$155.00	$155.00
Purchase #4	$182.39	3.866%	$189.4412	$189.44	$189.45	$189.40
Purchase #5	$85.45	6.477%	$90.9846	$90.98	$91.00	$91.00
Purchase #6	$106.84	3.323%	$110.3903	$110.39	$110.40	$110.40
Purchase #7	$146.72	3.232%	$151.462	$151.46	$151.45	$151.50
7 purchase totals =	$1,008.64		$1,065.9106	$1,065.91	$1,065.95	$1,066.00