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	$113.78	12.335%	$127.8148	$127.81	$127.80	$127.80
Purchase #2	$136.56	11.548%	$152.3299	$152.33	$152.35	$152.30
Purchase #3	$64.44	11.564%	$71.8918	$71.89	$71.90	$71.90
Purchase #4	$100.87	13.641%	$114.6297	$114.63	$114.65	$114.60
Purchase #5	$235.94	3.377%	$243.9077	$243.91	$243.90	$243.90
Purchase #6	$75.25	4.799%	$78.8612	$78.86	$78.85	$78.90
Purchase #7	$195.74	11.355%	$217.9663	$217.97	$217.95	$218.00
7 purchase totals =	$922.58		$1,007.4014	$1,007.40	$1,007.40	$1,007.40