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	$148.63	12.534%	$167.2593	$167.26	$167.25	$167.30
Purchase #2	$187.27	3.292%	$193.4349	$193.43	$193.45	$193.40
Purchase #3	$44.27	4.748%	$46.3719	$46.37	$46.35	$46.40
Purchase #4	$139.26	8.335%	$150.8673	$150.87	$150.85	$150.90
Purchase #5	$78.68	13.553%	$89.3435	$89.34	$89.35	$89.30
Purchase #6	$99.79	10.146%	$109.9147	$109.91	$109.90	$109.90
Purchase #7	$33.76	4.472%	$35.2697	$35.27	$35.25	$35.30
7 purchase totals =	$731.66		$792.4613	$792.45	$792.40	$792.50