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	$78.63	13.564%	$89.2954	$89.30	$89.30	$89.30
Purchase #2	$213.36	4.387%	$222.7201	$222.72	$222.70	$222.70
Purchase #3	$54.67	6.404%	$58.1711	$58.17	$58.15	$58.20
Purchase #4	$117.80	4.289%	$122.8524	$122.85	$122.85	$122.90
Purchase #5	$171.32	4.114%	$178.3681	$178.37	$178.35	$178.40
Purchase #6	$209.33	3.440%	$216.531	$216.53	$216.55	$216.50
Purchase #7	$202.64	7.301%	$217.4347	$217.43	$217.45	$217.40
7 purchase totals =	$1,047.75		$1,105.3728	$1,105.37	$1,105.35	$1,105.40