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	$53.56	10.776%	$59.3316	$59.33	$59.35	$59.30
Purchase #2	$88.74	9.496%	$97.1668	$97.17	$97.15	$97.20
Purchase #3	$134.95	3.210%	$139.2819	$139.28	$139.30	$139.30
Purchase #4	$31.61	13.329%	$35.8233	$35.82	$35.80	$35.80
Purchase #5	$35.66	5.216%	$37.52	$37.52	$37.50	$37.50
Purchase #6	$146.76	10.821%	$162.6409	$162.64	$162.65	$162.60
Purchase #7	$248.48	3.129%	$256.2549	$256.25	$256.25	$256.30
7 purchase totals =	$739.76		$788.0194	$788.01	$788.00	$788.00