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	$145.36	5.597%	$153.4958	$153.50	$153.50	$153.50
Purchase #2	$15.57	12.387%	$17.4987	$17.50	$17.50	$17.50
Purchase #3	$181.69	5.291%	$191.3032	$191.30	$191.30	$191.30
Purchase #4	$240.28	12.496%	$270.3054	$270.31	$270.30	$270.30
Purchase #5	$191.77	9.688%	$210.3487	$210.35	$210.35	$210.30
Purchase #6	$247.33	7.737%	$266.4659	$266.47	$266.45	$266.50
Purchase #7	$39.29	8.349%	$42.5703	$42.57	$42.55	$42.60
7 purchase totals =	$1,061.29		$1,151.9880	$1,152.00	$1,151.95	$1,152.00