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	$118.41	10.705%	$131.0858	$131.09	$131.10	$131.10
Purchase #2	$168.60	8.599%	$183.0979	$183.10	$183.10	$183.10
Purchase #3	$147.26	13.655%	$167.3684	$167.37	$167.35	$167.40
Purchase #4	$130.55	13.780%	$148.5398	$148.54	$148.55	$148.50
Purchase #5	$248.44	9.852%	$272.9163	$272.92	$272.90	$272.90
Purchase #6	$242.69	9.561%	$265.8936	$265.89	$265.90	$265.90
Purchase #7	$50.35	6.463%	$53.6041	$53.60	$53.60	$53.60
7 purchase totals =	$1,106.30		$1,222.5059	$1,222.51	$1,222.50	$1,222.50