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	$51.32	12.344%	$57.6549	$57.65	$57.65	$57.70
Purchase #2	$220.75	9.648%	$242.048	$242.05	$242.05	$242.00
Purchase #3	$192.57	9.133%	$210.1574	$210.16	$210.15	$210.20
Purchase #4	$85.71	4.685%	$89.7255	$89.73	$89.75	$89.70
Purchase #5	$72.62	5.790%	$76.8247	$76.82	$76.80	$76.80
Purchase #6	$225.58	3.540%	$233.5655	$233.57	$233.55	$233.60
Purchase #7	$95.67	3.719%	$99.228	$99.23	$99.25	$99.20
7 purchase totals =	$944.22		$1,009.2040	$1,009.21	$1,009.20	$1,009.20