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	$64.64	11.291%	$71.9385	$71.94	$71.95	$71.90
Purchase #2	$45.42	4.217%	$47.3354	$47.34	$47.35	$47.30
Purchase #3	$239.25	3.586%	$247.8295	$247.83	$247.85	$247.80
Purchase #4	$240.98	13.647%	$273.8665	$273.87	$273.85	$273.90
Purchase #5	$215.27	3.372%	$222.5289	$222.53	$222.55	$222.50
Purchase #6	$208.30	12.129%	$233.5647	$233.56	$233.55	$233.60
Purchase #7	$177.52	12.752%	$200.1574	$200.16	$200.15	$200.20
7 purchase totals =	$1,191.38		$1,297.2209	$1,297.23	$1,297.25	$1,297.20