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	$92.70	10.392%	$102.3334	$102.33	$102.35	$102.30
Purchase #2	$240.28	6.334%	$255.4993	$255.50	$255.50	$255.50
Purchase #3	$47.66	6.839%	$50.9195	$50.92	$50.90	$50.90
Purchase #4	$246.94	10.791%	$273.5873	$273.59	$273.60	$273.60
Purchase #5	$82.80	10.162%	$91.2141	$91.21	$91.20	$91.20
Purchase #6	$142.31	7.304%	$152.7043	$152.70	$152.70	$152.70
Purchase #7	$177.84	3.550%	$184.1533	$184.15	$184.15	$184.20
7 purchase totals =	$1,030.53		$1,110.4112	$1,110.40	$1,110.40	$1,110.40