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	$160.26	6.554%	$170.7634	$170.76	$170.75	$170.80
Purchase #2	$172.36	13.676%	$195.932	$195.93	$195.95	$195.90
Purchase #3	$219.28	13.250%	$248.3346	$248.33	$248.35	$248.30
Purchase #4	$90.61	10.808%	$100.4031	$100.40	$100.40	$100.40
Purchase #5	$135.73	13.327%	$153.8187	$153.82	$153.80	$153.80
Purchase #6	$100.84	10.723%	$111.6531	$111.65	$111.65	$111.70
Purchase #7	$147.94	11.364%	$164.7519	$164.75	$164.75	$164.80
7 purchase totals =	$1,027.02		$1,145.6568	$1,145.64	$1,145.65	$1,145.70