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	$140.58	8.191%	$152.0949	$152.09	$152.10	$152.10
Purchase #2	$115.54	11.241%	$128.5279	$128.53	$128.55	$128.50
Purchase #3	$134.43	3.773%	$139.502	$139.50	$139.50	$139.50
Purchase #4	$209.88	7.432%	$225.4783	$225.48	$225.50	$225.50
Purchase #5	$97.92	13.129%	$110.7759	$110.78	$110.80	$110.80
Purchase #6	$59.37	8.460%	$64.3927	$64.39	$64.40	$64.40
Purchase #7	$63.32	12.311%	$71.1153	$71.12	$71.10	$71.10
7 purchase totals =	$821.04		$891.8870	$891.89	$891.95	$891.90