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	$148.51	10.583%	$164.2268	$164.23	$164.25	$164.20
Purchase #2	$45.35	10.801%	$50.2483	$50.25	$50.25	$50.20
Purchase #3	$180.41	6.627%	$192.3658	$192.37	$192.35	$192.40
Purchase #4	$205.56	11.742%	$229.6969	$229.70	$229.70	$229.70
Purchase #5	$204.71	5.454%	$215.8749	$215.87	$215.85	$215.90
Purchase #6	$130.56	9.850%	$143.4202	$143.42	$143.40	$143.40
Purchase #7	$84.45	8.202%	$91.3766	$91.38	$91.40	$91.40
7 purchase totals =	$999.55		$1,087.2095	$1,087.22	$1,087.20	$1,087.20