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	$166.33	6.326%	$176.852	$176.85	$176.85	$176.90
Purchase #2	$183.60	7.107%	$196.6485	$196.65	$196.65	$196.60
Purchase #3	$196.73	9.842%	$216.0922	$216.09	$216.10	$216.10
Purchase #4	$230.96	12.473%	$259.7676	$259.77	$259.75	$259.80
Purchase #5	$67.37	13.219%	$76.2756	$76.28	$76.30	$76.30
Purchase #6	$43.84	5.243%	$46.1385	$46.14	$46.15	$46.10
Purchase #7	$173.55	6.808%	$185.3653	$185.37	$185.35	$185.40
7 purchase totals =	$1,062.38		$1,157.1397	$1,157.15	$1,157.15	$1,157.20