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	$59.33	9.515%	$64.9752	$64.98	$65.00	$65.00
Purchase #2	$111.98	13.611%	$127.2216	$127.22	$127.20	$127.20
Purchase #3	$157.76	11.522%	$175.9371	$175.94	$175.95	$175.90
Purchase #4	$221.69	4.773%	$232.2713	$232.27	$232.25	$232.30
Purchase #5	$38.51	4.807%	$40.3612	$40.36	$40.35	$40.40
Purchase #6	$189.86	7.733%	$204.5419	$204.54	$204.55	$204.50
Purchase #7	$64.82	3.522%	$67.103	$67.10	$67.10	$67.10
7 purchase totals =	$843.95		$912.4113	$912.41	$912.40	$912.40