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	$182.30	13.628%	$207.1438	$207.14	$207.15	$207.10
Purchase #2	$65.91	6.821%	$70.4057	$70.41	$70.40	$70.40
Purchase #3	$100.81	8.543%	$109.4222	$109.42	$109.40	$109.40
Purchase #4	$102.96	6.408%	$109.5577	$109.56	$109.55	$109.60
Purchase #5	$162.87	4.261%	$169.8099	$169.81	$169.80	$169.80
Purchase #6	$181.43	9.384%	$198.4554	$198.46	$198.45	$198.50
Purchase #7	$88.57	12.368%	$99.5243	$99.52	$99.50	$99.50
7 purchase totals =	$884.85		$964.3190	$964.32	$964.25	$964.30