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	$116.79	11.398%	$130.1017	$130.10	$130.10	$130.10
Purchase #2	$86.90	9.583%	$95.2276	$95.23	$95.25	$95.20
Purchase #3	$201.93	4.125%	$210.2596	$210.26	$210.25	$210.30
Purchase #4	$96.69	9.460%	$105.8369	$105.84	$105.85	$105.80
Purchase #5	$86.32	4.745%	$90.4159	$90.42	$90.40	$90.40
Purchase #6	$175.88	11.771%	$196.5828	$196.58	$196.60	$196.60
Purchase #7	$35.84	7.376%	$38.4836	$38.48	$38.50	$38.50
7 purchase totals =	$800.35		$866.9081	$866.91	$866.95	$866.90