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	$61.31	11.451%	$68.3306	$68.33	$68.35	$68.30
Purchase #2	$82.93	3.582%	$85.9006	$85.90	$85.90	$85.90
Purchase #3	$26.95	4.446%	$28.1482	$28.15	$28.15	$28.10
Purchase #4	$53.89	13.125%	$60.9631	$60.96	$60.95	$61.00
Purchase #5	$172.77	3.181%	$178.2658	$178.27	$178.25	$178.30
Purchase #6	$53.97	8.321%	$58.4608	$58.46	$58.45	$58.50
Purchase #7	$127.51	5.354%	$134.3369	$134.34	$134.35	$134.30
7 purchase totals =	$579.33		$614.4060	$614.41	$614.40	$614.40