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	$164.69	10.175%	$181.4472	$181.45	$181.45	$181.40
Purchase #2	$47.85	3.402%	$49.4779	$49.48	$49.50	$49.50
Purchase #3	$226.66	9.424%	$248.0204	$248.02	$248.00	$248.00
Purchase #4	$226.46	10.314%	$249.8171	$249.82	$249.80	$249.80
Purchase #5	$50.29	8.655%	$54.6426	$54.64	$54.65	$54.60
Purchase #6	$49.55	10.475%	$54.7404	$54.74	$54.75	$54.70
Purchase #7	$53.56	11.410%	$59.6712	$59.67	$59.65	$59.70
7 purchase totals =	$819.06		$897.8168	$897.82	$897.80	$897.70