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	$156.31	5.311%	$164.6116	$164.61	$164.60	$164.60
Purchase #2	$43.73	4.337%	$45.6266	$45.63	$45.65	$45.60
Purchase #3	$60.80	8.799%	$66.1498	$66.15	$66.15	$66.10
Purchase #4	$122.56	3.820%	$127.2418	$127.24	$127.25	$127.20
Purchase #5	$57.64	4.451%	$60.2056	$60.21	$60.20	$60.20
Purchase #6	$64.46	12.707%	$72.6509	$72.65	$72.65	$72.70
Purchase #7	$167.98	11.506%	$187.3078	$187.31	$187.30	$187.30
7 purchase totals =	$673.48		$723.7941	$723.80	$723.80	$723.70