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	$196.93	11.353%	$219.2875	$219.29	$219.30	$219.30
Purchase #2	$194.70	5.242%	$204.9062	$204.91	$204.90	$204.90
Purchase #3	$90.70	9.584%	$99.3927	$99.39	$99.40	$99.40
Purchase #4	$150.44	10.162%	$165.7277	$165.73	$165.75	$165.70
Purchase #5	$78.99	5.604%	$83.4166	$83.42	$83.40	$83.40
Purchase #6	$176.71	12.559%	$198.903	$198.90	$198.90	$198.90
Purchase #7	$248.51	7.399%	$266.8973	$266.90	$266.90	$266.90
7 purchase totals =	$1,136.98		$1,238.5310	$1,238.54	$1,238.55	$1,238.50