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	$112.97	3.460%	$116.8788	$116.88	$116.90	$116.90
Purchase #2	$236.88	10.364%	$261.4302	$261.43	$261.45	$261.40
Purchase #3	$217.53	13.359%	$246.5898	$246.59	$246.60	$246.60
Purchase #4	$167.32	11.446%	$186.4714	$186.47	$186.45	$186.50
Purchase #5	$100.55	5.705%	$106.2864	$106.29	$106.30	$106.30
Purchase #6	$86.78	10.759%	$96.1167	$96.12	$96.10	$96.10
Purchase #7	$139.48	13.107%	$157.7616	$157.76	$157.75	$157.80
7 purchase totals =	$1,061.51		$1,171.5349	$1,171.54	$1,171.55	$1,171.60