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	$102.58	8.594%	$111.3957	$111.40	$111.40	$111.40
Purchase #2	$54.68	8.259%	$59.196	$59.20	$59.20	$59.20
Purchase #3	$207.76	3.837%	$215.7318	$215.73	$215.75	$215.70
Purchase #4	$147.83	3.280%	$152.6788	$152.68	$152.70	$152.70
Purchase #5	$218.48	10.568%	$241.569	$241.57	$241.55	$241.60
Purchase #6	$128.74	10.103%	$141.7466	$141.75	$141.75	$141.70
Purchase #7	$163.33	6.790%	$174.4201	$174.42	$174.40	$174.40
7 purchase totals =	$1,023.40		$1,096.7380	$1,096.75	$1,096.75	$1,096.70