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	$33.71	11.452%	$37.5705	$37.57	$37.55	$37.60
Purchase #2	$170.93	6.404%	$181.8764	$181.88	$181.90	$181.90
Purchase #3	$89.45	6.463%	$95.2312	$95.23	$95.25	$95.20
Purchase #4	$228.73	8.797%	$248.8514	$248.85	$248.85	$248.90
Purchase #5	$210.96	9.860%	$231.7607	$231.76	$231.75	$231.80
Purchase #6	$213.54	5.605%	$225.5089	$225.51	$225.50	$225.50
Purchase #7	$117.81	7.703%	$126.8849	$126.88	$126.90	$126.90
7 purchase totals =	$1,065.13		$1,147.6840	$1,147.68	$1,147.70	$1,147.80