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	$236.26	9.230%	$258.0668	$258.07	$258.05	$258.10
Purchase #2	$82.54	9.242%	$90.1683	$90.17	$90.15	$90.20
Purchase #3	$21.72	13.317%	$24.6125	$24.61	$24.60	$24.60
Purchase #4	$249.36	5.545%	$263.187	$263.19	$263.20	$263.20
Purchase #5	$135.80	7.279%	$145.6849	$145.68	$145.70	$145.70
Purchase #6	$56.26	5.163%	$59.1647	$59.16	$59.15	$59.20
Purchase #7	$41.92	10.809%	$46.4511	$46.45	$46.45	$46.50
7 purchase totals =	$823.86		$887.3353	$887.33	$887.30	$887.50