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	$153.52	11.463%	$171.118	$171.12	$171.10	$171.10
Purchase #2	$243.41	4.168%	$253.5553	$253.56	$253.55	$253.60
Purchase #3	$32.89	11.247%	$36.5891	$36.59	$36.60	$36.60
Purchase #4	$206.61	9.784%	$226.8247	$226.82	$226.80	$226.80
Purchase #5	$176.49	11.367%	$196.5516	$196.55	$196.55	$196.60
Purchase #6	$229.56	13.520%	$260.5965	$260.60	$260.60	$260.60
Purchase #7	$180.50	8.831%	$196.44	$196.44	$196.45	$196.40
7 purchase totals =	$1,222.98		$1,341.6752	$1,341.68	$1,341.65	$1,341.70