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	$220.59	9.398%	$241.321	$241.32	$241.30	$241.30
Purchase #2	$45.99	12.745%	$51.8514	$51.85	$51.85	$51.90
Purchase #3	$147.57	12.590%	$166.1491	$166.15	$166.15	$166.10
Purchase #4	$218.82	4.209%	$228.0301	$228.03	$228.05	$228.00
Purchase #5	$47.70	11.404%	$53.1397	$53.14	$53.15	$53.10
Purchase #6	$58.92	13.278%	$66.7434	$66.74	$66.75	$66.70
Purchase #7	$42.27	7.129%	$45.2834	$45.28	$45.30	$45.30
7 purchase totals =	$781.86		$852.5181	$852.51	$852.55	$852.40