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	$166.93	11.129%	$185.5076	$185.51	$185.50	$185.50
Purchase #2	$118.87	12.184%	$133.3531	$133.35	$133.35	$133.40
Purchase #3	$210.34	13.139%	$237.9766	$237.98	$238.00	$238.00
Purchase #4	$71.50	13.214%	$80.948	$80.95	$80.95	$80.90
Purchase #5	$150.41	10.557%	$166.2888	$166.29	$166.30	$166.30
Purchase #6	$39.32	8.582%	$42.6944	$42.69	$42.70	$42.70
Purchase #7	$168.40	3.487%	$174.2721	$174.27	$174.25	$174.30
7 purchase totals =	$925.77		$1,021.0406	$1,021.04	$1,021.05	$1,021.10