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	$135.34	5.164%	$142.329	$142.33	$142.35	$142.30
Purchase #2	$165.52	10.172%	$182.3567	$182.36	$182.35	$182.40
Purchase #3	$96.88	12.339%	$108.834	$108.83	$108.85	$108.80
Purchase #4	$73.95	6.361%	$78.654	$78.65	$78.65	$78.70
Purchase #5	$106.43	5.471%	$112.2528	$112.25	$112.25	$112.30
Purchase #6	$34.62	7.609%	$37.2542	$37.25	$37.25	$37.30
Purchase #7	$177.76	8.189%	$192.3168	$192.32	$192.30	$192.30
7 purchase totals =	$790.50		$853.9975	$853.99	$854.00	$854.10