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	$243.58	6.828%	$260.2116	$260.21	$260.20	$260.20
Purchase #2	$233.77	12.254%	$262.4162	$262.42	$262.40	$262.40
Purchase #3	$198.72	11.870%	$222.3081	$222.31	$222.30	$222.30
Purchase #4	$143.69	3.230%	$148.3312	$148.33	$148.35	$148.30
Purchase #5	$88.81	8.693%	$96.5303	$96.53	$96.55	$96.50
Purchase #6	$140.96	4.524%	$147.337	$147.34	$147.35	$147.30
Purchase #7	$93.58	7.173%	$100.2925	$100.29	$100.30	$100.30
7 purchase totals =	$1,143.11		$1,237.4269	$1,237.43	$1,237.45	$1,237.30