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	$53.87	11.144%	$59.8733	$59.87	$59.85	$59.90
Purchase #2	$83.83	6.169%	$89.0015	$89.00	$89.00	$89.00
Purchase #3	$191.32	6.583%	$203.9146	$203.91	$203.90	$203.90
Purchase #4	$195.84	4.119%	$203.9066	$203.91	$203.90	$203.90
Purchase #5	$225.43	5.515%	$237.8625	$237.86	$237.85	$237.90
Purchase #6	$103.33	10.143%	$113.8108	$113.81	$113.80	$113.80
Purchase #7	$185.90	11.711%	$207.6707	$207.67	$207.65	$207.70
7 purchase totals =	$1,039.52		$1,116.0400	$1,116.03	$1,115.95	$1,116.10