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	$100.59	13.602%	$114.2723	$114.27	$114.25	$114.30
Purchase #2	$43.81	9.715%	$48.0661	$48.07	$48.05	$48.10
Purchase #3	$57.74	5.705%	$61.0341	$61.03	$61.05	$61.00
Purchase #4	$178.91	9.394%	$195.7168	$195.72	$195.70	$195.70
Purchase #5	$125.85	13.502%	$142.8423	$142.84	$142.85	$142.80
Purchase #6	$229.39	4.864%	$240.5475	$240.55	$240.55	$240.50
Purchase #7	$64.30	12.408%	$72.2783	$72.28	$72.30	$72.30
7 purchase totals =	$800.59		$874.7574	$874.76	$874.75	$874.70