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	$155.36	7.828%	$167.5216	$167.52	$167.50	$167.50
Purchase #2	$223.92	10.676%	$247.8257	$247.83	$247.85	$247.80
Purchase #3	$147.94	7.501%	$159.037	$159.04	$159.05	$159.00
Purchase #4	$87.77	5.448%	$92.5517	$92.55	$92.55	$92.60
Purchase #5	$187.40	9.545%	$205.2873	$205.29	$205.30	$205.30
Purchase #6	$136.48	4.689%	$142.8795	$142.88	$142.90	$142.90
Purchase #7	$63.85	10.454%	$70.5249	$70.52	$70.50	$70.50
7 purchase totals =	$1,002.72		$1,085.6277	$1,085.63	$1,085.65	$1,085.60