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	$52.39	12.790%	$59.0907	$59.09	$59.10	$59.10
Purchase #2	$233.72	11.657%	$260.9647	$260.96	$260.95	$261.00
Purchase #3	$92.74	7.340%	$99.5471	$99.55	$99.55	$99.50
Purchase #4	$131.64	7.728%	$141.8131	$141.81	$141.80	$141.80
Purchase #5	$245.48	7.663%	$264.2911	$264.29	$264.30	$264.30
Purchase #6	$160.36	7.718%	$172.7366	$172.74	$172.75	$172.70
Purchase #7	$111.96	3.226%	$115.5718	$115.57	$115.55	$115.60
7 purchase totals =	$1,028.29		$1,114.0151	$1,114.01	$1,114.00	$1,114.00