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	$163.37	3.695%	$169.4065	$169.41	$169.40	$169.40
Purchase #2	$37.60	11.715%	$42.0048	$42.00	$42.00	$42.00
Purchase #3	$220.47	9.579%	$241.5888	$241.59	$241.60	$241.60
Purchase #4	$5.40	13.572%	$6.1329	$6.13	$6.15	$6.10
Purchase #5	$129.95	11.142%	$144.429	$144.43	$144.45	$144.40
Purchase #6	$223.98	9.156%	$244.4876	$244.49	$244.50	$244.50
Purchase #7	$242.83	3.481%	$251.2829	$251.28	$251.30	$251.30
7 purchase totals =	$1,023.60		$1,099.3325	$1,099.33	$1,099.40	$1,099.30