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	$82.65	3.521%	$85.5601	$85.56	$85.55	$85.60
Purchase #2	$208.68	7.384%	$224.0889	$224.09	$224.10	$224.10
Purchase #3	$55.76	9.189%	$60.8838	$60.88	$60.90	$60.90
Purchase #4	$145.48	11.685%	$162.4793	$162.48	$162.50	$162.50
Purchase #5	$158.92	8.180%	$171.9197	$171.92	$171.90	$171.90
Purchase #6	$94.67	9.444%	$103.6106	$103.61	$103.60	$103.60
Purchase #7	$147.38	6.243%	$156.5809	$156.58	$156.60	$156.60
7 purchase totals =	$893.54		$965.1233	$965.12	$965.15	$965.20