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	$166.81	3.201%	$172.1496	$172.15	$172.15	$172.10
Purchase #2	$10.84	13.276%	$12.2791	$12.28	$12.30	$12.30
Purchase #3	$196.42	6.804%	$209.7844	$209.78	$209.80	$209.80
Purchase #4	$36.28	6.474%	$38.6288	$38.63	$38.65	$38.60
Purchase #5	$158.52	4.808%	$166.1416	$166.14	$166.15	$166.10
Purchase #6	$53.88	12.361%	$60.5401	$60.54	$60.55	$60.50
Purchase #7	$19.76	9.497%	$21.6366	$21.64	$21.65	$21.60
7 purchase totals =	$642.51		$681.1602	$681.16	$681.25	$681.00