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	$99.66	10.236%	$109.8612	$109.86	$109.85	$109.90
Purchase #2	$159.87	9.197%	$174.5732	$174.57	$174.55	$174.60
Purchase #3	$73.53	11.776%	$82.1889	$82.19	$82.20	$82.20
Purchase #4	$56.87	5.207%	$59.8312	$59.83	$59.85	$59.80
Purchase #5	$245.62	5.606%	$259.3895	$259.39	$259.40	$259.40
Purchase #6	$129.47	11.613%	$144.5054	$144.51	$144.50	$144.50
Purchase #7	$234.48	6.229%	$249.0858	$249.09	$249.10	$249.10
7 purchase totals =	$999.50		$1,079.4352	$1,079.44	$1,079.45	$1,079.50