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	$96.66	7.720%	$104.1222	$104.12	$104.10	$104.10
Purchase #2	$27.46	8.731%	$29.8575	$29.86	$29.85	$29.90
Purchase #3	$181.65	3.385%	$187.7989	$187.80	$187.80	$187.80
Purchase #4	$185.52	3.382%	$191.7943	$191.79	$191.80	$191.80
Purchase #5	$227.36	12.694%	$256.2211	$256.22	$256.20	$256.20
Purchase #6	$150.98	8.625%	$164.002	$164.00	$164.00	$164.00
Purchase #7	$67.73	4.259%	$70.6146	$70.61	$70.60	$70.60
7 purchase totals =	$937.36		$1,004.4106	$1,004.40	$1,004.35	$1,004.40