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	$166.95	7.569%	$179.5864	$179.59	$179.60	$179.60
Purchase #2	$197.83	12.661%	$222.8773	$222.88	$222.90	$222.90
Purchase #3	$183.55	9.361%	$200.7321	$200.73	$200.75	$200.70
Purchase #4	$120.55	5.480%	$127.1561	$127.16	$127.15	$127.20
Purchase #5	$219.87	11.320%	$244.7593	$244.76	$244.75	$244.80
Purchase #6	$96.28	3.207%	$99.3677	$99.37	$99.35	$99.40
Purchase #7	$40.71	8.737%	$44.2668	$44.27	$44.25	$44.30
7 purchase totals =	$1,025.74		$1,118.7457	$1,118.76	$1,118.75	$1,118.90