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	$154.66	3.357%	$159.8519	$159.85	$159.85	$159.90
Purchase #2	$221.29	9.112%	$241.4539	$241.45	$241.45	$241.50
Purchase #3	$97.33	11.789%	$108.8042	$108.80	$108.80	$108.80
Purchase #4	$174.50	12.805%	$196.8447	$196.84	$196.85	$196.80
Purchase #5	$208.61	6.652%	$222.4867	$222.49	$222.50	$222.50
Purchase #6	$219.54	8.508%	$238.2185	$238.22	$238.20	$238.20
Purchase #7	$234.61	6.799%	$250.5611	$250.56	$250.55	$250.60
7 purchase totals =	$1,310.54		$1,418.2210	$1,418.21	$1,418.20	$1,418.30