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	$193.42	6.234%	$205.4778	$205.48	$205.50	$205.50
Purchase #2	$131.66	7.365%	$141.3568	$141.36	$141.35	$141.40
Purchase #3	$74.36	5.799%	$78.6721	$78.67	$78.65	$78.70
Purchase #4	$170.75	10.270%	$188.286	$188.29	$188.30	$188.30
Purchase #5	$165.90	3.207%	$171.2204	$171.22	$171.20	$171.20
Purchase #6	$114.87	7.419%	$123.3922	$123.39	$123.40	$123.40
Purchase #7	$41.33	9.763%	$45.365	$45.37	$45.35	$45.40
7 purchase totals =	$892.29		$953.7703	$953.78	$953.75	$953.90