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	$179.29	11.173%	$199.3221	$199.32	$199.30	$199.30
Purchase #2	$76.62	5.701%	$80.9881	$80.99	$81.00	$81.00
Purchase #3	$37.49	6.427%	$39.8995	$39.90	$39.90	$39.90
Purchase #4	$144.55	11.744%	$161.526	$161.53	$161.55	$161.50
Purchase #5	$156.91	6.611%	$167.2833	$167.28	$167.30	$167.30
Purchase #6	$175.26	5.799%	$185.4233	$185.42	$185.40	$185.40
Purchase #7	$166.28	9.689%	$182.3909	$182.39	$182.40	$182.40
7 purchase totals =	$936.40		$1,016.8332	$1,016.83	$1,016.85	$1,016.80