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	$32.88	6.688%	$35.079	$35.08	$35.10	$35.10
Purchase #2	$162.56	13.506%	$184.5154	$184.52	$184.50	$184.50
Purchase #3	$241.56	11.176%	$268.5567	$268.56	$268.55	$268.60
Purchase #4	$150.31	12.322%	$168.8312	$168.83	$168.85	$168.80
Purchase #5	$206.97	5.562%	$218.4817	$218.48	$218.50	$218.50
Purchase #6	$33.48	12.604%	$37.6998	$37.70	$37.70	$37.70
Purchase #7	$119.56	13.547%	$135.7568	$135.76	$135.75	$135.80
7 purchase totals =	$947.32		$1,048.9206	$1,048.93	$1,048.95	$1,049.00