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	$186.78	13.470%	$211.9393	$211.94	$211.95	$211.90
Purchase #2	$84.41	12.416%	$94.8903	$94.89	$94.90	$94.90
Purchase #3	$74.89	9.679%	$82.1386	$82.14	$82.15	$82.10
Purchase #4	$187.66	9.646%	$205.7617	$205.76	$205.75	$205.80
Purchase #5	$37.36	11.489%	$41.6523	$41.65	$41.65	$41.70
Purchase #6	$92.91	12.734%	$104.7412	$104.74	$104.75	$104.70
Purchase #7	$118.60	4.458%	$123.8872	$123.89	$123.90	$123.90
7 purchase totals =	$782.61		$865.0106	$865.01	$865.05	$865.00