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	$152.25	10.742%	$168.6047	$168.60	$168.60	$168.60
Purchase #2	$101.73	12.764%	$114.7148	$114.71	$114.70	$114.70
Purchase #3	$53.27	3.652%	$55.2154	$55.22	$55.20	$55.20
Purchase #4	$113.27	6.776%	$120.9452	$120.95	$120.95	$120.90
Purchase #5	$82.25	8.846%	$89.5258	$89.53	$89.55	$89.50
Purchase #6	$145.59	10.146%	$160.3616	$160.36	$160.35	$160.40
Purchase #7	$94.79	11.189%	$105.3961	$105.40	$105.40	$105.40
7 purchase totals =	$743.15		$814.7636	$814.77	$814.75	$814.70