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	$82.35	10.455%	$90.9597	$90.96	$90.95	$91.00
Purchase #2	$62.50	6.118%	$66.3238	$66.32	$66.30	$66.30
Purchase #3	$219.97	3.544%	$227.7657	$227.77	$227.75	$227.80
Purchase #4	$219.92	13.512%	$249.6356	$249.64	$249.65	$249.60
Purchase #5	$58.91	13.584%	$66.9123	$66.91	$66.90	$66.90
Purchase #6	$229.90	6.535%	$244.924	$244.92	$244.90	$244.90
Purchase #7	$99.84	5.491%	$105.3222	$105.32	$105.30	$105.30
7 purchase totals =	$973.39		$1,051.8433	$1,051.84	$1,051.75	$1,051.80