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	$20.47	11.151%	$22.7526	$22.75	$22.75	$22.80
Purchase #2	$13.74	4.362%	$14.3393	$14.34	$14.35	$14.30
Purchase #3	$86.94	5.518%	$91.7373	$91.74	$91.75	$91.70
Purchase #4	$129.49	10.781%	$143.4503	$143.45	$143.45	$143.50
Purchase #5	$222.61	7.850%	$240.0849	$240.08	$240.10	$240.10
Purchase #6	$28.62	11.438%	$31.8936	$31.89	$31.90	$31.90
Purchase #7	$93.33	6.593%	$99.4832	$99.48	$99.50	$99.50
7 purchase totals =	$595.20		$643.7412	$643.73	$643.80	$643.80