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	$149.32	10.799%	$165.4451	$165.45	$165.45	$165.40
Purchase #2	$74.56	5.622%	$78.7518	$78.75	$78.75	$78.80
Purchase #3	$130.79	9.158%	$142.7677	$142.77	$142.75	$142.80
Purchase #4	$117.68	8.239%	$127.3757	$127.38	$127.40	$127.40
Purchase #5	$25.47	9.182%	$27.8087	$27.81	$27.80	$27.80
Purchase #6	$207.71	12.355%	$233.3726	$233.37	$233.35	$233.40
Purchase #7	$140.26	11.552%	$156.4628	$156.46	$156.45	$156.50
7 purchase totals =	$845.79		$931.9844	$931.99	$931.95	$932.10