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	$195.84	6.305%	$208.1877	$208.19	$208.20	$208.20
Purchase #2	$197.46	12.542%	$222.2254	$222.23	$222.25	$222.20
Purchase #3	$184.82	5.739%	$195.4268	$195.43	$195.45	$195.40
Purchase #4	$6.85	6.537%	$7.2978	$7.30	$7.30	$7.30
Purchase #5	$78.46	13.448%	$89.0113	$89.01	$89.00	$89.00
Purchase #6	$192.37	9.811%	$211.2434	$211.24	$211.25	$211.20
Purchase #7	$66.35	5.658%	$70.1041	$70.10	$70.10	$70.10
7 purchase totals =	$922.15		$1,003.4965	$1,003.50	$1,003.55	$1,003.40