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	$41.25	11.164%	$45.8552	$45.86	$45.85	$45.90
Purchase #2	$88.31	5.103%	$92.8165	$92.82	$92.80	$92.80
Purchase #3	$85.95	13.298%	$97.3796	$97.38	$97.40	$97.40
Purchase #4	$38.45	5.349%	$40.5067	$40.51	$40.50	$40.50
Purchase #5	$250.93	13.585%	$285.0188	$285.02	$285.00	$285.00
Purchase #6	$58.64	9.706%	$64.3316	$64.33	$64.35	$64.30
Purchase #7	$163.40	13.758%	$185.8806	$185.88	$185.90	$185.90
7 purchase totals =	$726.93		$811.7890	$811.80	$811.80	$811.80