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	$75.48	9.476%	$82.6325	$82.63	$82.65	$82.60
Purchase #2	$206.78	3.446%	$213.9056	$213.91	$213.90	$213.90
Purchase #3	$216.77	3.713%	$224.8187	$224.82	$224.80	$224.80
Purchase #4	$250.26	7.179%	$268.2262	$268.23	$268.25	$268.20
Purchase #5	$48.46	4.689%	$50.7323	$50.73	$50.75	$50.70
Purchase #6	$121.53	10.745%	$134.5884	$134.59	$134.60	$134.60
Purchase #7	$185.32	6.272%	$196.9433	$196.94	$196.95	$196.90
7 purchase totals =	$1,104.60		$1,171.8470	$1,171.85	$1,171.90	$1,171.70