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	$77.51	10.207%	$85.4214	$85.42	$85.40	$85.40
Purchase #2	$171.76	5.630%	$181.4301	$181.43	$181.45	$181.40
Purchase #3	$89.72	11.359%	$99.9113	$99.91	$99.90	$99.90
Purchase #4	$195.44	6.532%	$208.2061	$208.21	$208.20	$208.20
Purchase #5	$149.81	12.578%	$168.6531	$168.65	$168.65	$168.70
Purchase #6	$154.41	4.781%	$161.7923	$161.79	$161.80	$161.80
Purchase #7	$150.32	11.658%	$167.8443	$167.84	$167.85	$167.80
7 purchase totals =	$988.97		$1,073.2586	$1,073.25	$1,073.25	$1,073.20