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	$239.83	7.641%	$258.1554	$258.16	$258.15	$258.20
Purchase #2	$98.55	6.563%	$105.0178	$105.02	$105.00	$105.00
Purchase #3	$205.82	9.610%	$225.5993	$225.60	$225.60	$225.60
Purchase #4	$173.40	10.532%	$191.6625	$191.66	$191.65	$191.70
Purchase #5	$89.47	13.841%	$101.8535	$101.85	$101.85	$101.90
Purchase #6	$82.63	8.248%	$89.4453	$89.45	$89.45	$89.40
Purchase #7	$228.66	4.483%	$238.9108	$238.91	$238.90	$238.90
7 purchase totals =	$1,118.36		$1,210.6446	$1,210.65	$1,210.60	$1,210.70