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	$153.41	6.153%	$162.8493	$162.85	$162.85	$162.80
Purchase #2	$87.52	3.155%	$90.2813	$90.28	$90.30	$90.30
Purchase #3	$245.86	8.562%	$266.9105	$266.91	$266.90	$266.90
Purchase #4	$182.96	9.650%	$200.6156	$200.62	$200.60	$200.60
Purchase #5	$93.33	4.872%	$97.877	$97.88	$97.90	$97.90
Purchase #6	$128.60	8.411%	$139.4165	$139.42	$139.40	$139.40
Purchase #7	$141.40	5.390%	$149.0215	$149.02	$149.00	$149.00
7 purchase totals =	$1,033.08		$1,106.9717	$1,106.98	$1,106.95	$1,106.90