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	$53.38	11.474%	$59.5048	$59.50	$59.50	$59.50
Purchase #2	$238.91	13.513%	$271.1939	$271.19	$271.20	$271.20
Purchase #3	$163.32	13.722%	$185.7308	$185.73	$185.75	$185.70
Purchase #4	$146.89	4.336%	$153.2592	$153.26	$153.25	$153.30
Purchase #5	$87.53	12.848%	$98.7759	$98.78	$98.80	$98.80
Purchase #6	$94.36	4.208%	$98.3307	$98.33	$98.35	$98.30
Purchase #7	$204.29	11.757%	$228.3084	$228.31	$228.30	$228.30
7 purchase totals =	$988.68		$1,095.1037	$1,095.10	$1,095.15	$1,095.10