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	$151.42	13.542%	$171.9253	$171.93	$171.95	$171.90
Purchase #2	$136.71	12.732%	$154.1159	$154.12	$154.10	$154.10
Purchase #3	$89.26	12.837%	$100.7183	$100.72	$100.70	$100.70
Purchase #4	$112.70	7.135%	$120.7411	$120.74	$120.75	$120.70
Purchase #5	$249.68	6.243%	$265.2675	$265.27	$265.25	$265.30
Purchase #6	$42.82	5.838%	$45.3198	$45.32	$45.30	$45.30
Purchase #7	$61.44	8.602%	$66.7251	$66.73	$66.75	$66.70
7 purchase totals =	$844.03		$924.8130	$924.83	$924.80	$924.70