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	$174.53	12.586%	$196.4963	$196.50	$196.50	$196.50
Purchase #2	$98.46	5.161%	$103.5415	$103.54	$103.55	$103.50
Purchase #3	$164.59	6.801%	$175.7838	$175.78	$175.80	$175.80
Purchase #4	$50.37	3.607%	$52.1868	$52.19	$52.20	$52.20
Purchase #5	$28.80	12.850%	$32.5008	$32.50	$32.50	$32.50
Purchase #6	$16.25	11.529%	$18.1235	$18.12	$18.10	$18.10
Purchase #7	$30.93	11.773%	$34.5714	$34.57	$34.55	$34.60
7 purchase totals =	$563.93		$613.2041	$613.20	$613.20	$613.20