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	$11.71	4.747%	$12.2659	$12.27	$12.25	$12.30
Purchase #2	$91.88	9.745%	$100.8337	$100.83	$100.85	$100.80
Purchase #3	$28.57	13.513%	$32.4307	$32.43	$32.45	$32.40
Purchase #4	$73.46	11.822%	$82.1444	$82.14	$82.15	$82.10
Purchase #5	$219.47	9.492%	$240.3021	$240.30	$240.30	$240.30
Purchase #6	$203.76	10.427%	$225.0061	$225.01	$225.00	$225.00
Purchase #7	$62.67	9.470%	$68.6048	$68.60	$68.60	$68.60
7 purchase totals =	$691.52		$761.5877	$761.58	$761.60	$761.50