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	$69.40	6.866%	$74.165	$74.17	$74.15	$74.20
Purchase #2	$153.65	13.502%	$174.3958	$174.40	$174.40	$174.40
Purchase #3	$88.46	5.432%	$93.2651	$93.27	$93.25	$93.30
Purchase #4	$42.52	11.817%	$47.5446	$47.54	$47.55	$47.50
Purchase #5	$123.34	7.408%	$132.477	$132.48	$132.50	$132.50
Purchase #6	$137.54	7.702%	$148.1333	$148.13	$148.15	$148.10
Purchase #7	$86.81	4.659%	$90.8545	$90.85	$90.85	$90.90
7 purchase totals =	$701.72		$760.8353	$760.84	$760.85	$760.90