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	$245.71	3.606%	$254.5703	$254.57	$254.55	$254.60
Purchase #2	$46.79	11.715%	$52.2714	$52.27	$52.25	$52.30
Purchase #3	$83.33	10.802%	$92.3313	$92.33	$92.35	$92.30
Purchase #4	$130.60	11.781%	$145.986	$145.99	$146.00	$146.00
Purchase #5	$240.77	6.136%	$255.5436	$255.54	$255.55	$255.50
Purchase #6	$35.81	13.780%	$40.7446	$40.74	$40.75	$40.70
Purchase #7	$86.47	9.557%	$94.7339	$94.73	$94.75	$94.70
7 purchase totals =	$869.48		$936.1811	$936.17	$936.20	$936.10