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	$71.33	11.287%	$79.381	$79.38	$79.40	$79.40
Purchase #2	$89.66	10.503%	$99.077	$99.08	$99.10	$99.10
Purchase #3	$230.67	10.686%	$255.3194	$255.32	$255.30	$255.30
Purchase #4	$233.35	7.398%	$250.6132	$250.61	$250.60	$250.60
Purchase #5	$136.59	6.466%	$145.4219	$145.42	$145.40	$145.40
Purchase #6	$189.66	4.584%	$198.354	$198.35	$198.35	$198.40
Purchase #7	$53.91	6.119%	$57.2088	$57.21	$57.20	$57.20
7 purchase totals =	$1,005.17		$1,085.3753	$1,085.37	$1,085.35	$1,085.40