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	$84.82	5.215%	$89.2434	$89.24	$89.25	$89.20
Purchase #2	$223.51	9.265%	$244.2182	$244.22	$244.20	$244.20
Purchase #3	$244.88	11.565%	$273.2004	$273.20	$273.20	$273.20
Purchase #4	$200.78	3.828%	$208.4659	$208.47	$208.45	$208.50
Purchase #5	$119.36	5.397%	$125.8019	$125.80	$125.80	$125.80
Purchase #6	$75.54	9.288%	$82.5562	$82.56	$82.55	$82.60
Purchase #7	$48.78	3.158%	$50.3205	$50.32	$50.30	$50.30
7 purchase totals =	$997.67		$1,073.8065	$1,073.81	$1,073.75	$1,073.80