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	$196.82	12.459%	$221.3418	$221.34	$221.35	$221.30
Purchase #2	$108.36	13.483%	$122.9702	$122.97	$122.95	$123.00
Purchase #3	$225.40	7.449%	$242.19	$242.19	$242.20	$242.20
Purchase #4	$92.26	13.769%	$104.9633	$104.96	$104.95	$105.00
Purchase #5	$84.82	6.794%	$90.5827	$90.58	$90.60	$90.60
Purchase #6	$80.69	10.712%	$89.3335	$89.33	$89.35	$89.30
Purchase #7	$232.96	11.675%	$260.1581	$260.16	$260.15	$260.20
7 purchase totals =	$1,021.31		$1,131.5396	$1,131.53	$1,131.55	$1,131.60