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	$220.73	12.585%	$248.5089	$248.51	$248.50	$248.50
Purchase #2	$35.63	12.788%	$40.1864	$40.19	$40.20	$40.20
Purchase #3	$147.44	9.526%	$161.4851	$161.49	$161.50	$161.50
Purchase #4	$194.25	4.626%	$203.236	$203.24	$203.25	$203.20
Purchase #5	$99.59	12.738%	$112.2758	$112.28	$112.30	$112.30
Purchase #6	$150.40	12.326%	$168.9383	$168.94	$168.95	$168.90
Purchase #7	$141.62	3.466%	$146.5285	$146.53	$146.55	$146.50
7 purchase totals =	$989.66		$1,081.1590	$1,081.18	$1,081.25	$1,081.10