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	$55.56	11.295%	$61.8355	$61.84	$61.85	$61.80
Purchase #2	$7.76	6.158%	$8.2379	$8.24	$8.25	$8.20
Purchase #3	$39.82	4.221%	$41.5008	$41.50	$41.50	$41.50
Purchase #4	$82.83	4.851%	$86.8481	$86.85	$86.85	$86.80
Purchase #5	$34.56	3.479%	$35.7623	$35.76	$35.75	$35.80
Purchase #6	$87.57	13.597%	$99.4769	$99.48	$99.50	$99.50
Purchase #7	$196.36	11.124%	$218.2031	$218.20	$218.20	$218.20
7 purchase totals =	$504.46		$551.8646	$551.87	$551.90	$551.80