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	$243.45	8.748%	$264.747	$264.75	$264.75	$264.70
Purchase #2	$82.26	6.224%	$87.3799	$87.38	$87.40	$87.40
Purchase #3	$230.96	10.834%	$255.9822	$255.98	$256.00	$256.00
Purchase #4	$115.72	6.399%	$123.1249	$123.12	$123.10	$123.10
Purchase #5	$18.71	12.472%	$21.0435	$21.04	$21.05	$21.00
Purchase #6	$225.32	13.425%	$255.5692	$255.57	$255.55	$255.60
Purchase #7	$55.68	6.724%	$59.4239	$59.42	$59.40	$59.40
7 purchase totals =	$972.10		$1,067.2706	$1,067.26	$1,067.25	$1,067.20