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	$149.94	7.706%	$161.4944	$161.49	$161.50	$161.50
Purchase #2	$139.90	4.173%	$145.738	$145.74	$145.75	$145.70
Purchase #3	$68.42	3.797%	$71.0179	$71.02	$71.00	$71.00
Purchase #4	$57.35	3.337%	$59.2638	$59.26	$59.25	$59.30
Purchase #5	$149.95	8.308%	$162.4078	$162.41	$162.40	$162.40
Purchase #6	$179.31	7.388%	$192.5574	$192.56	$192.55	$192.60
Purchase #7	$43.29	4.640%	$45.2987	$45.30	$45.30	$45.30
7 purchase totals =	$788.16		$837.7780	$837.78	$837.75	$837.80