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	$242.76	10.127%	$267.3443	$267.34	$267.35	$267.30
Purchase #2	$86.26	4.414%	$90.0675	$90.07	$90.05	$90.10
Purchase #3	$221.72	10.640%	$245.311	$245.31	$245.30	$245.30
Purchase #4	$233.76	6.636%	$249.2723	$249.27	$249.25	$249.30
Purchase #5	$184.81	6.124%	$196.1278	$196.13	$196.15	$196.10
Purchase #6	$90.88	4.228%	$94.7224	$94.72	$94.70	$94.70
Purchase #7	$92.82	8.384%	$100.602	$100.60	$100.60	$100.60
7 purchase totals =	$1,153.01		$1,243.4473	$1,243.44	$1,243.40	$1,243.40