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	$186.35	5.453%	$196.5117	$196.51	$196.50	$196.50
Purchase #2	$129.67	3.539%	$134.259	$134.26	$134.25	$134.30
Purchase #3	$165.65	7.465%	$178.0158	$178.02	$178.00	$178.00
Purchase #4	$235.28	6.202%	$249.8721	$249.87	$249.85	$249.90
Purchase #5	$52.93	11.257%	$58.8883	$58.89	$58.90	$58.90
Purchase #6	$25.72	6.787%	$27.4656	$27.47	$27.45	$27.50
Purchase #7	$243.75	9.191%	$266.1531	$266.15	$266.15	$266.20
7 purchase totals =	$1,039.35		$1,111.1656	$1,111.17	$1,111.10	$1,111.30