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	$144.57	10.276%	$159.426	$159.43	$159.45	$159.40
Purchase #2	$17.40	3.860%	$18.0716	$18.07	$18.05	$18.10
Purchase #3	$91.96	6.672%	$98.0956	$98.10	$98.10	$98.10
Purchase #4	$77.90	9.549%	$85.3387	$85.34	$85.35	$85.30
Purchase #5	$244.84	12.171%	$274.6395	$274.64	$274.65	$274.60
Purchase #6	$39.30	10.181%	$43.3011	$43.30	$43.30	$43.30
Purchase #7	$147.97	13.308%	$167.6618	$167.66	$167.65	$167.70
7 purchase totals =	$763.94		$846.5343	$846.54	$846.55	$846.50