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	$111.97	11.539%	$124.8902	$124.89	$124.90	$124.90
Purchase #2	$100.44	5.199%	$105.6619	$105.66	$105.65	$105.70
Purchase #3	$170.85	6.764%	$182.4063	$182.41	$182.40	$182.40
Purchase #4	$59.38	7.650%	$63.9226	$63.92	$63.90	$63.90
Purchase #5	$161.44	3.731%	$167.4633	$167.46	$167.45	$167.50
Purchase #6	$223.51	11.789%	$249.8596	$249.86	$249.85	$249.90
Purchase #7	$147.91	5.296%	$155.7433	$155.74	$155.75	$155.70
7 purchase totals =	$975.50		$1,049.9472	$1,049.94	$1,049.90	$1,050.00