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	$177.82	4.331%	$185.5214	$185.52	$185.50	$185.50
Purchase #2	$180.62	4.657%	$189.0315	$189.03	$189.05	$189.00
Purchase #3	$94.54	6.614%	$100.7929	$100.79	$100.80	$100.80
Purchase #4	$141.40	10.501%	$156.2484	$156.25	$156.25	$156.20
Purchase #5	$207.79	6.840%	$222.0028	$222.00	$222.00	$222.00
Purchase #6	$60.84	8.557%	$66.0461	$66.05	$66.05	$66.00
Purchase #7	$185.43	3.318%	$191.5826	$191.58	$191.60	$191.60
7 purchase totals =	$1,048.44		$1,111.2257	$1,111.22	$1,111.25	$1,111.10