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	$111.98	10.347%	$123.5666	$123.57	$123.55	$123.60
Purchase #2	$193.82	11.613%	$216.3283	$216.33	$216.35	$216.30
Purchase #3	$74.41	6.185%	$79.0123	$79.01	$79.00	$79.00
Purchase #4	$128.63	8.174%	$139.1442	$139.14	$139.15	$139.10
Purchase #5	$47.51	7.372%	$51.0124	$51.01	$51.00	$51.00
Purchase #6	$147.82	13.379%	$167.5968	$167.60	$167.60	$167.60
Purchase #7	$69.99	12.809%	$78.955	$78.96	$78.95	$79.00
7 purchase totals =	$774.16		$855.6156	$855.62	$855.60	$855.60