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	$77.25	6.617%	$82.3616	$82.36	$82.35	$82.40
Purchase #2	$165.31	10.138%	$182.0691	$182.07	$182.05	$182.10
Purchase #3	$88.81	10.622%	$98.2434	$98.24	$98.25	$98.20
Purchase #4	$234.69	12.707%	$264.5121	$264.51	$264.50	$264.50
Purchase #5	$45.61	13.222%	$51.6406	$51.64	$51.65	$51.60
Purchase #6	$121.66	6.520%	$129.5922	$129.59	$129.60	$129.60
Purchase #7	$59.98	7.175%	$64.2836	$64.28	$64.30	$64.30
7 purchase totals =	$793.31		$872.7026	$872.69	$872.70	$872.70