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	$162.53	11.282%	$180.8666	$180.87	$180.85	$180.90
Purchase #2	$137.69	9.470%	$150.7292	$150.73	$150.75	$150.70
Purchase #3	$94.44	6.715%	$100.7816	$100.78	$100.80	$100.80
Purchase #4	$168.88	9.799%	$185.4286	$185.43	$185.45	$185.40
Purchase #5	$153.79	12.600%	$173.1675	$173.17	$173.15	$173.20
Purchase #6	$24.40	9.182%	$26.6404	$26.64	$26.65	$26.60
Purchase #7	$234.28	9.158%	$255.7354	$255.74	$255.75	$255.70
7 purchase totals =	$976.01		$1,073.3493	$1,073.36	$1,073.40	$1,073.30