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	$137.58	10.389%	$151.8732	$151.87	$151.85	$151.90
Purchase #2	$64.50	8.174%	$69.7722	$69.77	$69.75	$69.80
Purchase #3	$133.75	7.658%	$143.9926	$143.99	$144.00	$144.00
Purchase #4	$130.49	7.212%	$139.9009	$139.90	$139.90	$139.90
Purchase #5	$131.25	8.426%	$142.3091	$142.31	$142.30	$142.30
Purchase #6	$227.76	10.174%	$250.9323	$250.93	$250.95	$250.90
Purchase #7	$137.63	4.741%	$144.155	$144.16	$144.15	$144.20
7 purchase totals =	$962.96		$1,042.9353	$1,042.93	$1,042.90	$1,043.00