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	$45.86	6.800%	$48.9785	$48.98	$49.00	$49.00
Purchase #2	$84.53	5.582%	$89.2485	$89.25	$89.25	$89.20
Purchase #3	$224.75	13.280%	$254.5968	$254.60	$254.60	$254.60
Purchase #4	$141.58	9.851%	$155.527	$155.53	$155.55	$155.50
Purchase #5	$183.97	13.115%	$208.0977	$208.10	$208.10	$208.10
Purchase #6	$176.56	4.362%	$184.2615	$184.26	$184.25	$184.30
Purchase #7	$219.61	9.477%	$240.4224	$240.42	$240.40	$240.40
7 purchase totals =	$1,076.86		$1,181.1324	$1,181.14	$1,181.15	$1,181.10