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	$154.25	7.249%	$165.4316	$165.43	$165.45	$165.40
Purchase #2	$69.63	3.345%	$71.9591	$71.96	$71.95	$72.00
Purchase #3	$240.36	4.104%	$250.2244	$250.22	$250.20	$250.20
Purchase #4	$98.80	6.664%	$105.384	$105.38	$105.40	$105.40
Purchase #5	$154.74	10.108%	$170.3811	$170.38	$170.40	$170.40
Purchase #6	$102.51	7.211%	$109.902	$109.90	$109.90	$109.90
Purchase #7	$90.32	12.553%	$101.6579	$101.66	$101.65	$101.70
7 purchase totals =	$910.61		$974.9401	$974.93	$974.95	$975.00