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	$31.82	5.764%	$33.6541	$33.65	$33.65	$33.70
Purchase #2	$157.79	5.207%	$166.0061	$166.01	$166.00	$166.00
Purchase #3	$229.60	4.758%	$240.5244	$240.52	$240.50	$240.50
Purchase #4	$125.29	12.586%	$141.059	$141.06	$141.05	$141.10
Purchase #5	$187.48	3.381%	$193.8187	$193.82	$193.80	$193.80
Purchase #6	$156.67	10.411%	$172.9809	$172.98	$173.00	$173.00
Purchase #7	$127.90	12.835%	$144.316	$144.32	$144.30	$144.30
7 purchase totals =	$1,016.55		$1,092.3592	$1,092.36	$1,092.30	$1,092.40