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	$200.58	10.439%	$221.5185	$221.52	$221.50	$221.50
Purchase #2	$99.48	3.826%	$103.2861	$103.29	$103.30	$103.30
Purchase #3	$156.72	6.596%	$167.0573	$167.06	$167.05	$167.10
Purchase #4	$213.84	11.224%	$237.8414	$237.84	$237.85	$237.80
Purchase #5	$189.52	11.402%	$211.1291	$211.13	$211.15	$211.10
Purchase #6	$101.47	11.471%	$113.1096	$113.11	$113.10	$113.10
Purchase #7	$117.67	11.698%	$131.435	$131.44	$131.45	$131.40
7 purchase totals =	$1,079.28		$1,185.3770	$1,185.39	$1,185.40	$1,185.30