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	$14.31	10.107%	$15.7563	$15.76	$15.75	$15.80
Purchase #2	$119.95	6.473%	$127.7144	$127.71	$127.70	$127.70
Purchase #3	$249.50	6.290%	$265.1936	$265.19	$265.20	$265.20
Purchase #4	$89.59	12.472%	$100.7637	$100.76	$100.75	$100.80
Purchase #5	$223.71	11.444%	$249.3114	$249.31	$249.30	$249.30
Purchase #6	$156.45	8.354%	$169.5198	$169.52	$169.50	$169.50
Purchase #7	$138.58	12.781%	$156.2919	$156.29	$156.30	$156.30
7 purchase totals =	$992.09		$1,084.5511	$1,084.54	$1,084.50	$1,084.60