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	$85.56	10.798%	$94.7988	$94.80	$94.80	$94.80
Purchase #2	$57.72	11.358%	$64.2758	$64.28	$64.30	$64.30
Purchase #3	$236.40	3.614%	$244.9435	$244.94	$244.95	$244.90
Purchase #4	$189.27	11.694%	$211.4032	$211.40	$211.40	$211.40
Purchase #5	$196.40	6.171%	$208.5198	$208.52	$208.50	$208.50
Purchase #6	$180.26	10.466%	$199.126	$199.13	$199.15	$199.10
Purchase #7	$74.99	10.147%	$82.5992	$82.60	$82.60	$82.60
7 purchase totals =	$1,020.60		$1,105.6663	$1,105.67	$1,105.70	$1,105.60