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	$245.41	4.238%	$255.8105	$255.81	$255.80	$255.80
Purchase #2	$37.78	8.672%	$41.0563	$41.06	$41.05	$41.10
Purchase #3	$67.78	4.770%	$71.0131	$71.01	$71.00	$71.00
Purchase #4	$181.49	3.393%	$187.648	$187.65	$187.65	$187.60
Purchase #5	$188.35	10.169%	$207.5033	$207.50	$207.50	$207.50
Purchase #6	$102.30	12.550%	$115.1387	$115.14	$115.15	$115.10
Purchase #7	$195.91	13.393%	$222.1482	$222.15	$222.15	$222.10
7 purchase totals =	$1,019.02		$1,100.3181	$1,100.32	$1,100.30	$1,100.20