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	$207.63	9.781%	$227.9383	$227.94	$227.95	$227.90
Purchase #2	$151.75	4.190%	$158.1083	$158.11	$158.10	$158.10
Purchase #3	$33.56	5.174%	$35.2964	$35.30	$35.30	$35.30
Purchase #4	$142.87	12.418%	$160.6116	$160.61	$160.60	$160.60
Purchase #5	$235.65	4.341%	$245.8796	$245.88	$245.90	$245.90
Purchase #6	$92.88	7.583%	$99.9231	$99.92	$99.90	$99.90
Purchase #7	$153.33	5.553%	$161.8444	$161.84	$161.85	$161.80
7 purchase totals =	$1,017.67		$1,089.6017	$1,089.60	$1,089.60	$1,089.50