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	$206.45	12.140%	$231.513	$231.51	$231.50	$231.50
Purchase #2	$173.54	7.273%	$186.1616	$186.16	$186.15	$186.20
Purchase #3	$17.52	4.846%	$18.369	$18.37	$18.35	$18.40
Purchase #4	$206.85	12.661%	$233.0393	$233.04	$233.05	$233.00
Purchase #5	$188.43	6.347%	$200.3897	$200.39	$200.40	$200.40
Purchase #6	$209.31	6.200%	$222.2872	$222.29	$222.30	$222.30
Purchase #7	$207.30	10.822%	$229.734	$229.73	$229.75	$229.70
7 purchase totals =	$1,209.40		$1,321.4938	$1,321.49	$1,321.50	$1,321.50