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	$183.47	4.390%	$191.5243	$191.52	$191.50	$191.50
Purchase #2	$161.51	5.552%	$170.477	$170.48	$170.50	$170.50
Purchase #3	$11.51	12.411%	$12.9385	$12.94	$12.95	$12.90
Purchase #4	$245.76	7.117%	$263.2507	$263.25	$263.25	$263.30
Purchase #5	$144.39	5.430%	$152.2304	$152.23	$152.25	$152.20
Purchase #6	$98.57	3.621%	$102.1392	$102.14	$102.15	$102.10
Purchase #7	$6.75	10.674%	$7.4705	$7.47	$7.45	$7.50
7 purchase totals =	$851.96		$900.0306	$900.03	$900.05	$900.00