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	$33.69	10.680%	$37.2881	$37.29	$37.30	$37.30
Purchase #2	$89.35	3.776%	$92.7239	$92.72	$92.70	$92.70
Purchase #3	$92.56	9.264%	$101.1348	$101.13	$101.15	$101.10
Purchase #4	$105.86	4.789%	$110.9296	$110.93	$110.95	$110.90
Purchase #5	$187.27	13.503%	$212.5571	$212.56	$212.55	$212.60
Purchase #6	$182.45	5.236%	$192.0031	$192.00	$192.00	$192.00
Purchase #7	$250.33	7.712%	$269.6354	$269.64	$269.65	$269.60
7 purchase totals =	$941.51		$1,016.2720	$1,016.27	$1,016.30	$1,016.20