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	$116.76	5.547%	$123.2367	$123.24	$123.25	$123.20
Purchase #2	$229.47	11.261%	$255.3106	$255.31	$255.30	$255.30
Purchase #3	$245.85	4.431%	$256.7436	$256.74	$256.75	$256.70
Purchase #4	$72.55	7.796%	$78.206	$78.21	$78.20	$78.20
Purchase #5	$12.40	13.834%	$14.1154	$14.12	$14.10	$14.10
Purchase #6	$35.75	9.475%	$39.1373	$39.14	$39.15	$39.10
Purchase #7	$162.78	13.508%	$184.7683	$184.77	$184.75	$184.80
7 purchase totals =	$875.56		$951.5179	$951.53	$951.50	$951.40