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	$182.59	8.144%	$197.4601	$197.46	$197.45	$197.50
Purchase #2	$80.48	13.475%	$91.3247	$91.32	$91.30	$91.30
Purchase #3	$202.59	3.661%	$210.0068	$210.01	$210.00	$210.00
Purchase #4	$108.57	3.247%	$112.0953	$112.10	$112.10	$112.10
Purchase #5	$202.29	7.511%	$217.484	$217.48	$217.50	$217.50
Purchase #6	$151.76	7.322%	$162.8719	$162.87	$162.85	$162.90
Purchase #7	$88.61	3.737%	$91.9214	$91.92	$91.90	$91.90
7 purchase totals =	$1,016.89		$1,083.1642	$1,083.16	$1,083.10	$1,083.20