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	$196.42	5.596%	$207.4117	$207.41	$207.40	$207.40
Purchase #2	$77.45	6.698%	$82.6376	$82.64	$82.65	$82.60
Purchase #3	$216.76	7.161%	$232.2822	$232.28	$232.30	$232.30
Purchase #4	$136.56	8.825%	$148.6114	$148.61	$148.60	$148.60
Purchase #5	$46.61	9.581%	$51.0757	$51.08	$51.10	$51.10
Purchase #6	$130.33	8.430%	$141.3168	$141.32	$141.30	$141.30
Purchase #7	$127.95	9.858%	$140.5633	$140.56	$140.55	$140.60
7 purchase totals =	$932.08		$1,003.8987	$1,003.90	$1,003.90	$1,003.90