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	$228.86	6.374%	$243.4475	$243.45	$243.45	$243.40
Purchase #2	$102.78	11.457%	$114.5555	$114.56	$114.55	$114.60
Purchase #3	$213.69	8.326%	$231.4818	$231.48	$231.50	$231.50
Purchase #4	$111.73	7.659%	$120.2874	$120.29	$120.30	$120.30
Purchase #5	$66.46	13.209%	$75.2387	$75.24	$75.25	$75.20
Purchase #6	$244.83	13.329%	$277.4634	$277.46	$277.45	$277.50
Purchase #7	$47.79	13.159%	$54.0787	$54.08	$54.10	$54.10
7 purchase totals =	$1,016.14		$1,116.5530	$1,116.56	$1,116.60	$1,116.60