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	$198.32	12.140%	$222.396	$222.40	$222.40	$222.40
Purchase #2	$26.82	3.327%	$27.7123	$27.71	$27.70	$27.70
Purchase #3	$36.35	3.849%	$37.7491	$37.75	$37.75	$37.70
Purchase #4	$125.62	5.274%	$132.2452	$132.25	$132.25	$132.20
Purchase #5	$135.63	4.396%	$141.5923	$141.59	$141.60	$141.60
Purchase #6	$175.61	7.425%	$188.649	$188.65	$188.65	$188.60
Purchase #7	$98.56	12.870%	$111.2447	$111.24	$111.25	$111.20
7 purchase totals =	$796.91		$861.5886	$861.59	$861.60	$861.40