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	$229.57	11.611%	$256.2254	$256.23	$256.25	$256.20
Purchase #2	$71.43	6.780%	$76.273	$76.27	$76.25	$76.30
Purchase #3	$189.61	13.670%	$215.5297	$215.53	$215.55	$215.50
Purchase #4	$118.39	10.844%	$131.2282	$131.23	$131.25	$131.20
Purchase #5	$118.71	3.655%	$123.0489	$123.05	$123.05	$123.00
Purchase #6	$109.68	10.237%	$120.9079	$120.91	$120.90	$120.90
Purchase #7	$185.61	4.453%	$193.8752	$193.88	$193.90	$193.90
7 purchase totals =	$1,023.00		$1,117.0883	$1,117.10	$1,117.15	$1,117.00