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	$205.31	13.702%	$233.4416	$233.44	$233.45	$233.40
Purchase #2	$118.63	8.627%	$128.8642	$128.86	$128.85	$128.90
Purchase #3	$154.77	7.439%	$166.2833	$166.28	$166.30	$166.30
Purchase #4	$230.47	8.455%	$249.9562	$249.96	$249.95	$250.00
Purchase #5	$98.78	8.142%	$106.8227	$106.82	$106.80	$106.80
Purchase #6	$224.89	11.306%	$250.3161	$250.32	$250.30	$250.30
Purchase #7	$40.71	11.671%	$45.4613	$45.46	$45.45	$45.50
7 purchase totals =	$1,073.56		$1,181.1454	$1,181.14	$1,181.10	$1,181.20