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	$72.80	6.460%	$77.5029	$77.50	$77.50	$77.50
Purchase #2	$26.42	7.198%	$28.3217	$28.32	$28.30	$28.30
Purchase #3	$156.44	6.305%	$166.3035	$166.30	$166.30	$166.30
Purchase #4	$145.75	4.734%	$152.6498	$152.65	$152.65	$152.60
Purchase #5	$70.36	3.242%	$72.6411	$72.64	$72.65	$72.60
Purchase #6	$68.56	8.865%	$74.6378	$74.64	$74.65	$74.60
Purchase #7	$181.27	10.528%	$200.3541	$200.35	$200.35	$200.40
7 purchase totals =	$721.60		$772.4109	$772.40	$772.40	$772.30