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	$65.72	10.130%	$72.3774	$72.38	$72.40	$72.40
Purchase #2	$145.58	5.313%	$153.3147	$153.31	$153.30	$153.30
Purchase #3	$25.29	11.827%	$28.281	$28.28	$28.30	$28.30
Purchase #4	$158.89	12.671%	$179.023	$179.02	$179.00	$179.00
Purchase #5	$174.47	13.846%	$198.6271	$198.63	$198.65	$198.60
Purchase #6	$115.52	10.375%	$127.5052	$127.51	$127.50	$127.50
Purchase #7	$246.49	9.808%	$270.6657	$270.67	$270.65	$270.70
7 purchase totals =	$931.96		$1,029.7941	$1,029.80	$1,029.80	$1,029.80