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	$50.53	6.103%	$53.6138	$53.61	$53.60	$53.60
Purchase #2	$202.55	5.597%	$213.8867	$213.89	$213.90	$213.90
Purchase #3	$41.34	10.456%	$45.6625	$45.66	$45.65	$45.70
Purchase #4	$244.66	10.689%	$270.8117	$270.81	$270.80	$270.80
Purchase #5	$163.88	4.738%	$171.6446	$171.64	$171.65	$171.60
Purchase #6	$64.88	12.664%	$73.0964	$73.10	$73.10	$73.10
Purchase #7	$223.72	4.693%	$234.2192	$234.22	$234.20	$234.20
7 purchase totals =	$991.56		$1,062.9349	$1,062.93	$1,062.90	$1,062.90