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	$82.75	5.469%	$87.2756	$87.28	$87.30	$87.30
Purchase #2	$36.39	4.111%	$37.886	$37.89	$37.90	$37.90
Purchase #3	$235.60	9.481%	$257.9372	$257.94	$257.95	$257.90
Purchase #4	$108.39	9.481%	$118.6665	$118.67	$118.65	$118.70
Purchase #5	$96.31	7.145%	$103.1913	$103.19	$103.20	$103.20
Purchase #6	$223.29	3.593%	$231.3128	$231.31	$231.30	$231.30
Purchase #7	$50.55	6.522%	$53.8469	$53.85	$53.85	$53.80
7 purchase totals =	$833.28		$890.1163	$890.13	$890.15	$890.10