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	$102.62	8.287%	$111.1241	$111.12	$111.10	$111.10
Purchase #2	$112.25	7.178%	$120.3073	$120.31	$120.30	$120.30
Purchase #3	$189.96	4.724%	$198.9337	$198.93	$198.95	$198.90
Purchase #4	$199.56	3.173%	$205.892	$205.89	$205.90	$205.90
Purchase #5	$51.51	12.297%	$57.8442	$57.84	$57.85	$57.80
Purchase #6	$62.63	10.666%	$69.3101	$69.31	$69.30	$69.30
Purchase #7	$73.50	11.749%	$82.1355	$82.14	$82.15	$82.10
7 purchase totals =	$792.03		$845.5469	$845.54	$845.55	$845.40