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	$118.66	7.662%	$127.7517	$127.75	$127.75	$127.80
Purchase #2	$47.76	5.309%	$50.2956	$50.30	$50.30	$50.30
Purchase #3	$176.74	6.325%	$187.9188	$187.92	$187.90	$187.90
Purchase #4	$120.44	8.828%	$131.0724	$131.07	$131.05	$131.10
Purchase #5	$222.80	9.723%	$244.4628	$244.46	$244.45	$244.50
Purchase #6	$216.45	11.290%	$240.8872	$240.89	$240.90	$240.90
Purchase #7	$167.47	3.695%	$173.658	$173.66	$173.65	$173.70
7 purchase totals =	$1,070.32		$1,156.0465	$1,156.05	$1,156.00	$1,156.20