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	$59.77	9.768%	$65.6083	$65.61	$65.60	$65.60
Purchase #2	$185.64	5.749%	$196.3124	$196.31	$196.30	$196.30
Purchase #3	$139.26	8.104%	$150.5456	$150.55	$150.55	$150.50
Purchase #4	$156.30	11.148%	$173.7243	$173.72	$173.70	$173.70
Purchase #5	$101.38	4.815%	$106.2614	$106.26	$106.25	$106.30
Purchase #6	$63.69	12.726%	$71.7952	$71.80	$71.80	$71.80
Purchase #7	$169.83	8.614%	$184.4592	$184.46	$184.45	$184.50
7 purchase totals =	$875.87		$948.7064	$948.71	$948.65	$948.70