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	$235.58	11.553%	$262.7966	$262.80	$262.80	$262.80
Purchase #2	$62.89	8.683%	$68.3507	$68.35	$68.35	$68.40
Purchase #3	$97.77	7.314%	$104.9209	$104.92	$104.90	$104.90
Purchase #4	$80.77	10.728%	$89.435	$89.44	$89.45	$89.40
Purchase #5	$109.33	10.447%	$120.7517	$120.75	$120.75	$120.80
Purchase #6	$140.80	6.482%	$149.9267	$149.93	$149.95	$149.90
Purchase #7	$231.46	10.298%	$255.2958	$255.30	$255.30	$255.30
7 purchase totals =	$958.60		$1,051.4774	$1,051.49	$1,051.50	$1,051.50