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	$173.73	13.343%	$196.9108	$196.91	$196.90	$196.90
Purchase #2	$175.25	6.799%	$187.1652	$187.17	$187.15	$187.20
Purchase #3	$20.31	12.421%	$22.8327	$22.83	$22.85	$22.80
Purchase #4	$100.32	4.565%	$104.8996	$104.90	$104.90	$104.90
Purchase #5	$125.55	7.159%	$134.5381	$134.54	$134.55	$134.50
Purchase #6	$112.68	12.807%	$127.1109	$127.11	$127.10	$127.10
Purchase #7	$196.52	9.476%	$215.1422	$215.14	$215.15	$215.10
7 purchase totals =	$904.36		$988.5995	$988.60	$988.60	$988.50