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	$97.50	12.566%	$109.7519	$109.75	$109.75	$109.80
Purchase #2	$168.86	3.209%	$174.2787	$174.28	$174.30	$174.30
Purchase #3	$35.52	13.636%	$40.3635	$40.36	$40.35	$40.40
Purchase #4	$41.52	10.682%	$45.9552	$45.96	$45.95	$46.00
Purchase #5	$89.30	10.865%	$99.0024	$99.00	$99.00	$99.00
Purchase #6	$48.91	4.408%	$51.066	$51.07	$51.05	$51.10
Purchase #7	$197.91	10.591%	$218.8706	$218.87	$218.85	$218.90
7 purchase totals =	$679.52		$739.2883	$739.29	$739.25	$739.50