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	$38.33	5.520%	$40.4458	$40.45	$40.45	$40.40
Purchase #2	$32.85	4.234%	$34.2409	$34.24	$34.25	$34.20
Purchase #3	$98.27	11.520%	$109.5907	$109.59	$109.60	$109.60
Purchase #4	$244.26	7.479%	$262.5282	$262.53	$262.55	$262.50
Purchase #5	$55.79	3.488%	$57.736	$57.74	$57.75	$57.70
Purchase #6	$76.71	8.469%	$83.2066	$83.21	$83.20	$83.20
Purchase #7	$214.51	3.665%	$222.3718	$222.37	$222.35	$222.40
7 purchase totals =	$760.72		$810.1200	$810.13	$810.15	$810.00