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	$189.40	6.106%	$200.9648	$200.96	$200.95	$201.00
Purchase #2	$197.37	5.509%	$208.2431	$208.24	$208.25	$208.20
Purchase #3	$158.94	10.139%	$175.0549	$175.05	$175.05	$175.10
Purchase #4	$33.44	11.734%	$37.3638	$37.36	$37.35	$37.40
Purchase #5	$19.73	10.716%	$21.8443	$21.84	$21.85	$21.80
Purchase #6	$119.72	10.121%	$131.8369	$131.84	$131.85	$131.80
Purchase #7	$239.27	10.661%	$264.7786	$264.78	$264.80	$264.80
7 purchase totals =	$957.87		$1,040.0864	$1,040.07	$1,040.10	$1,040.10