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	$231.32	8.835%	$251.7571	$251.76	$251.75	$251.80
Purchase #2	$52.67	13.131%	$59.5861	$59.59	$59.60	$59.60
Purchase #3	$236.68	3.277%	$244.436	$244.44	$244.45	$244.40
Purchase #4	$131.29	12.587%	$147.8155	$147.82	$147.80	$147.80
Purchase #5	$142.92	13.674%	$162.4629	$162.46	$162.45	$162.50
Purchase #6	$218.38	13.367%	$247.5709	$247.57	$247.55	$247.60
Purchase #7	$49.37	6.366%	$52.5129	$52.51	$52.50	$52.50
7 purchase totals =	$1,062.63		$1,166.1414	$1,166.15	$1,166.10	$1,166.20