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	$133.49	4.241%	$139.1513	$139.15	$139.15	$139.20
Purchase #2	$165.97	4.761%	$173.8718	$173.87	$173.85	$173.90
Purchase #3	$177.68	7.808%	$191.5533	$191.55	$191.55	$191.60
Purchase #4	$157.81	6.231%	$167.6431	$167.64	$167.65	$167.60
Purchase #5	$101.46	7.325%	$108.8919	$108.89	$108.90	$108.90
Purchase #6	$129.66	7.636%	$139.5608	$139.56	$139.55	$139.60
Purchase #7	$215.33	4.139%	$224.2425	$224.24	$224.25	$224.20
7 purchase totals =	$1,081.40		$1,144.9147	$1,144.90	$1,144.90	$1,145.00