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	$52.38	6.192%	$55.6234	$55.62	$55.60	$55.60
Purchase #2	$87.39	4.289%	$91.1382	$91.14	$91.15	$91.10
Purchase #3	$35.77	5.402%	$37.7023	$37.70	$37.70	$37.70
Purchase #4	$250.99	13.789%	$285.599	$285.60	$285.60	$285.60
Purchase #5	$92.54	4.333%	$96.5498	$96.55	$96.55	$96.50
Purchase #6	$207.96	4.774%	$217.888	$217.89	$217.90	$217.90
Purchase #7	$93.58	6.539%	$99.6992	$99.70	$99.70	$99.70
7 purchase totals =	$820.61		$884.1999	$884.20	$884.20	$884.10