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	$107.60	4.872%	$112.8423	$112.84	$112.85	$112.80
Purchase #2	$93.53	6.183%	$99.313	$99.31	$99.30	$99.30
Purchase #3	$124.69	7.640%	$134.2163	$134.22	$134.20	$134.20
Purchase #4	$79.48	9.213%	$86.8025	$86.80	$86.80	$86.80
Purchase #5	$207.52	8.799%	$225.7797	$225.78	$225.80	$225.80
Purchase #6	$32.96	13.235%	$37.3223	$37.32	$37.30	$37.30
Purchase #7	$71.70	6.365%	$76.2637	$76.26	$76.25	$76.30
7 purchase totals =	$717.48		$772.5398	$772.53	$772.50	$772.50