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	$61.67	9.596%	$67.5879	$67.59	$67.60	$67.60
Purchase #2	$47.43	7.843%	$51.1499	$51.15	$51.15	$51.10
Purchase #3	$241.99	13.134%	$273.773	$273.77	$273.75	$273.80
Purchase #4	$83.55	9.669%	$91.6284	$91.63	$91.65	$91.60
Purchase #5	$196.53	13.483%	$223.0281	$223.03	$223.05	$223.00
Purchase #6	$179.35	11.613%	$200.1779	$200.18	$200.20	$200.20
Purchase #7	$105.99	5.722%	$112.0547	$112.05	$112.05	$112.10
7 purchase totals =	$916.51		$1,019.3999	$1,019.40	$1,019.45	$1,019.40