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	$200.51	12.715%	$226.0048	$226.00	$226.00	$226.00
Purchase #2	$73.64	11.730%	$82.278	$82.28	$82.30	$82.30
Purchase #3	$50.56	6.385%	$53.7883	$53.79	$53.80	$53.80
Purchase #4	$70.59	11.141%	$78.4544	$78.45	$78.45	$78.50
Purchase #5	$211.51	13.497%	$240.0575	$240.06	$240.05	$240.10
Purchase #6	$198.36	4.737%	$207.7563	$207.76	$207.75	$207.80
Purchase #7	$186.61	6.278%	$198.3254	$198.33	$198.35	$198.30
7 purchase totals =	$991.78		$1,086.6647	$1,086.67	$1,086.70	$1,086.80