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	$223.94	11.426%	$249.5274	$249.53	$249.55	$249.50
Purchase #2	$26.32	4.746%	$27.5691	$27.57	$27.55	$27.60
Purchase #3	$138.96	10.203%	$153.1381	$153.14	$153.15	$153.10
Purchase #4	$80.31	12.295%	$90.1841	$90.18	$90.20	$90.20
Purchase #5	$214.63	9.498%	$235.0156	$235.02	$235.00	$235.00
Purchase #6	$92.53	13.487%	$105.0095	$105.01	$105.00	$105.00
Purchase #7	$165.76	5.212%	$174.3994	$174.40	$174.40	$174.40
7 purchase totals =	$942.45		$1,034.8432	$1,034.85	$1,034.85	$1,034.80