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	$77.72	3.474%	$80.42	$80.42	$80.40	$80.40
Purchase #2	$154.71	9.230%	$168.9897	$168.99	$169.00	$169.00
Purchase #3	$168.54	8.348%	$182.6097	$182.61	$182.60	$182.60
Purchase #4	$143.79	6.295%	$152.8416	$152.84	$152.85	$152.80
Purchase #5	$67.76	6.563%	$72.2071	$72.21	$72.20	$72.20
Purchase #6	$185.72	3.663%	$192.5229	$192.52	$192.50	$192.50
Purchase #7	$217.37	11.347%	$242.035	$242.04	$242.05	$242.00
7 purchase totals =	$1,015.61		$1,091.6260	$1,091.63	$1,091.60	$1,091.50