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	$168.55	10.701%	$186.5865	$186.59	$186.60	$186.60
Purchase #2	$86.58	3.805%	$89.8744	$89.87	$89.85	$89.90
Purchase #3	$189.66	10.868%	$210.2722	$210.27	$210.25	$210.30
Purchase #4	$79.64	12.625%	$89.6946	$89.69	$89.70	$89.70
Purchase #5	$84.38	12.388%	$94.833	$94.83	$94.85	$94.80
Purchase #6	$238.42	12.672%	$268.6326	$268.63	$268.65	$268.60
Purchase #7	$149.62	8.593%	$162.4768	$162.48	$162.50	$162.50
7 purchase totals =	$996.85		$1,102.3701	$1,102.36	$1,102.40	$1,102.40