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	$34.80	4.688%	$36.4314	$36.43	$36.45	$36.40
Purchase #2	$152.50	6.657%	$162.6519	$162.65	$162.65	$162.70
Purchase #3	$165.27	9.199%	$180.4732	$180.47	$180.45	$180.50
Purchase #4	$38.86	6.222%	$41.2779	$41.28	$41.30	$41.30
Purchase #5	$173.48	4.461%	$181.2189	$181.22	$181.20	$181.20
Purchase #6	$138.73	4.114%	$144.4374	$144.44	$144.45	$144.40
Purchase #7	$208.31	7.489%	$223.9103	$223.91	$223.90	$223.90
7 purchase totals =	$911.95		$970.4010	$970.40	$970.40	$970.40