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	$137.73	8.495%	$149.4302	$149.43	$149.45	$149.40
Purchase #2	$219.76	13.427%	$249.2672	$249.27	$249.25	$249.30
Purchase #3	$130.36	11.195%	$144.9538	$144.95	$144.95	$145.00
Purchase #4	$32.69	13.384%	$37.0652	$37.07	$37.05	$37.10
Purchase #5	$96.79	9.364%	$105.8534	$105.85	$105.85	$105.90
Purchase #6	$131.40	12.712%	$148.1036	$148.10	$148.10	$148.10
Purchase #7	$164.76	6.718%	$175.8286	$175.83	$175.85	$175.80
7 purchase totals =	$913.49		$1,010.5020	$1,010.50	$1,010.50	$1,010.60