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	$162.45	9.325%	$177.5985	$177.60	$177.60	$177.60
Purchase #2	$87.44	13.238%	$99.0153	$99.02	$99.00	$99.00
Purchase #3	$227.35	10.181%	$250.4965	$250.50	$250.50	$250.50
Purchase #4	$87.66	4.346%	$91.4697	$91.47	$91.45	$91.50
Purchase #5	$162.29	5.573%	$171.3344	$171.33	$171.35	$171.30
Purchase #6	$198.36	3.418%	$205.1399	$205.14	$205.15	$205.10
Purchase #7	$234.63	3.780%	$243.499	$243.50	$243.50	$243.50
7 purchase totals =	$1,160.18		$1,238.5533	$1,238.56	$1,238.55	$1,238.50