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	$76.33	13.201%	$86.4063	$86.41	$86.40	$86.40
Purchase #2	$177.32	11.372%	$197.4848	$197.48	$197.50	$197.50
Purchase #3	$84.38	6.102%	$89.5289	$89.53	$89.55	$89.50
Purchase #4	$238.78	10.151%	$263.0186	$263.02	$263.00	$263.00
Purchase #5	$109.26	8.513%	$118.5613	$118.56	$118.55	$118.60
Purchase #6	$148.87	11.407%	$165.8516	$165.85	$165.85	$165.90
Purchase #7	$67.78	4.456%	$70.8003	$70.80	$70.80	$70.80
7 purchase totals =	$902.72		$991.6518	$991.65	$991.65	$991.70