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	$72.70	4.666%	$76.0922	$76.09	$76.10	$76.10
Purchase #2	$134.52	10.228%	$148.2787	$148.28	$148.30	$148.30
Purchase #3	$167.31	3.469%	$173.114	$173.11	$173.10	$173.10
Purchase #4	$91.64	11.177%	$101.8826	$101.88	$101.90	$101.90
Purchase #5	$192.27	3.209%	$198.4399	$198.44	$198.45	$198.40
Purchase #6	$197.86	11.135%	$219.8917	$219.89	$219.90	$219.90
Purchase #7	$187.90	6.584%	$200.2713	$200.27	$200.25	$200.30
7 purchase totals =	$1,044.20		$1,117.9704	$1,117.96	$1,118.00	$1,118.00