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	$232.48	13.109%	$262.9558	$262.96	$262.95	$263.00
Purchase #2	$126.46	11.722%	$141.2836	$141.28	$141.30	$141.30
Purchase #3	$130.48	9.437%	$142.7934	$142.79	$142.80	$142.80
Purchase #4	$82.59	8.788%	$89.848	$89.85	$89.85	$89.80
Purchase #5	$37.79	8.844%	$41.1321	$41.13	$41.15	$41.10
Purchase #6	$149.47	6.269%	$158.8403	$158.84	$158.85	$158.80
Purchase #7	$231.51	10.354%	$255.4805	$255.48	$255.50	$255.50
7 purchase totals =	$990.78		$1,092.3337	$1,092.33	$1,092.40	$1,092.30