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	$229.63	3.512%	$237.6946	$237.69	$237.70	$237.70
Purchase #2	$57.28	7.753%	$61.7209	$61.72	$61.70	$61.70
Purchase #3	$215.34	4.606%	$225.2586	$225.26	$225.25	$225.30
Purchase #4	$248.45	4.464%	$259.5408	$259.54	$259.55	$259.50
Purchase #5	$207.34	3.831%	$215.2832	$215.28	$215.30	$215.30
Purchase #6	$43.75	7.470%	$47.0181	$47.02	$47.00	$47.00
Purchase #7	$134.29	11.742%	$150.0583	$150.06	$150.05	$150.10
7 purchase totals =	$1,136.08		$1,196.5745	$1,196.57	$1,196.55	$1,196.60