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	$179.69	10.575%	$198.6922	$198.69	$198.70	$198.70
Purchase #2	$208.39	9.705%	$228.6142	$228.61	$228.60	$228.60
Purchase #3	$110.33	13.846%	$125.6063	$125.61	$125.60	$125.60
Purchase #4	$78.83	4.375%	$82.2788	$82.28	$82.30	$82.30
Purchase #5	$197.39	4.132%	$205.5462	$205.55	$205.55	$205.50
Purchase #6	$28.76	9.775%	$31.5713	$31.57	$31.55	$31.60
Purchase #7	$233.26	3.444%	$241.2935	$241.29	$241.30	$241.30
7 purchase totals =	$1,036.65		$1,113.6025	$1,113.60	$1,113.60	$1,113.60