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	$208.62	8.282%	$225.8979	$225.90	$225.90	$225.90
Purchase #2	$79.65	7.346%	$85.5011	$85.50	$85.50	$85.50
Purchase #3	$217.85	11.296%	$242.4583	$242.46	$242.45	$242.50
Purchase #4	$37.30	13.720%	$42.4176	$42.42	$42.40	$42.40
Purchase #5	$191.71	11.115%	$213.0186	$213.02	$213.00	$213.00
Purchase #6	$145.91	7.141%	$156.3294	$156.33	$156.35	$156.30
Purchase #7	$49.48	6.625%	$52.7581	$52.76	$52.75	$52.80
7 purchase totals =	$930.52		$1,018.3810	$1,018.39	$1,018.35	$1,018.40