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	$69.67	7.135%	$74.641	$74.64	$74.65	$74.60
Purchase #2	$77.39	6.572%	$82.4761	$82.48	$82.50	$82.50
Purchase #3	$76.38	5.319%	$80.4427	$80.44	$80.45	$80.40
Purchase #4	$57.55	3.845%	$59.7628	$59.76	$59.75	$59.80
Purchase #5	$246.33	3.869%	$255.8605	$255.86	$255.85	$255.90
Purchase #6	$222.89	3.604%	$230.923	$230.92	$230.90	$230.90
Purchase #7	$123.94	3.423%	$128.1825	$128.18	$128.20	$128.20
7 purchase totals =	$874.15		$912.2886	$912.28	$912.30	$912.30