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	$82.48	7.529%	$88.6899	$88.69	$88.70	$88.70
Purchase #2	$214.89	5.380%	$226.4511	$226.45	$226.45	$226.50
Purchase #3	$157.75	5.568%	$166.5335	$166.53	$166.55	$166.50
Purchase #4	$101.41	9.718%	$111.265	$111.27	$111.25	$111.30
Purchase #5	$156.41	6.169%	$166.0589	$166.06	$166.05	$166.10
Purchase #6	$174.81	7.762%	$188.3788	$188.38	$188.40	$188.40
Purchase #7	$154.75	13.165%	$175.1228	$175.12	$175.10	$175.10
7 purchase totals =	$1,042.50		$1,122.5000	$1,122.50	$1,122.50	$1,122.60