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	$143.75	6.520%	$153.1225	$153.12	$153.10	$153.10
Purchase #2	$174.27	12.614%	$196.2524	$196.25	$196.25	$196.30
Purchase #3	$196.79	6.364%	$209.3137	$209.31	$209.30	$209.30
Purchase #4	$18.66	13.683%	$21.2132	$21.21	$21.20	$21.20
Purchase #5	$95.73	8.555%	$103.9197	$103.92	$103.90	$103.90
Purchase #6	$131.73	8.536%	$142.9745	$142.97	$142.95	$143.00
Purchase #7	$177.54	10.115%	$195.4982	$195.50	$195.50	$195.50
7 purchase totals =	$938.47		$1,022.2942	$1,022.28	$1,022.20	$1,022.30