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	$171.54	9.131%	$187.2033	$187.20	$187.20	$187.20
Purchase #2	$81.77	4.223%	$85.2231	$85.22	$85.20	$85.20
Purchase #3	$136.70	9.605%	$149.83	$149.83	$149.85	$149.80
Purchase #4	$136.74	10.232%	$150.7312	$150.73	$150.75	$150.70
Purchase #5	$156.39	11.635%	$174.586	$174.59	$174.60	$174.60
Purchase #6	$25.25	9.522%	$27.6543	$27.65	$27.65	$27.70
Purchase #7	$65.82	10.478%	$72.7166	$72.72	$72.70	$72.70
7 purchase totals =	$774.21		$847.9445	$847.94	$847.95	$847.90