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	$184.61	12.725%	$208.1016	$208.10	$208.10	$208.10
Purchase #2	$80.79	10.843%	$89.5501	$89.55	$89.55	$89.60
Purchase #3	$35.89	6.155%	$38.099	$38.10	$38.10	$38.10
Purchase #4	$169.97	9.866%	$186.7392	$186.74	$186.75	$186.70
Purchase #5	$195.96	3.343%	$202.5109	$202.51	$202.50	$202.50
Purchase #6	$121.47	4.740%	$127.2277	$127.23	$127.25	$127.20
Purchase #7	$193.42	9.435%	$211.6692	$211.67	$211.65	$211.70
7 purchase totals =	$982.11		$1,063.8977	$1,063.90	$1,063.90	$1,063.90