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	$144.66	7.323%	$155.2535	$155.25	$155.25	$155.30
Purchase #2	$142.62	6.653%	$152.1085	$152.11	$152.10	$152.10
Purchase #3	$137.43	9.314%	$150.2302	$150.23	$150.25	$150.20
Purchase #4	$178.62	9.822%	$196.1641	$196.16	$196.15	$196.20
Purchase #5	$161.38	13.564%	$183.2696	$183.27	$183.25	$183.30
Purchase #6	$210.80	12.381%	$236.8991	$236.90	$236.90	$236.90
Purchase #7	$13.25	5.325%	$13.9556	$13.96	$13.95	$14.00
7 purchase totals =	$988.76		$1,087.8806	$1,087.88	$1,087.85	$1,088.00