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	$170.93	5.275%	$179.9466	$179.95	$179.95	$179.90
Purchase #2	$181.86	8.235%	$196.8362	$196.84	$196.85	$196.80
Purchase #3	$97.35	13.676%	$110.6636	$110.66	$110.65	$110.70
Purchase #4	$146.98	13.623%	$167.0031	$167.00	$167.00	$167.00
Purchase #5	$37.98	11.640%	$42.4009	$42.40	$42.40	$42.40
Purchase #6	$189.30	3.837%	$196.5634	$196.56	$196.55	$196.60
Purchase #7	$58.98	7.354%	$63.3174	$63.32	$63.30	$63.30
7 purchase totals =	$883.38		$956.7312	$956.73	$956.70	$956.70