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	$181.88	12.312%	$204.2731	$204.27	$204.25	$204.30
Purchase #2	$75.54	3.135%	$77.9082	$77.91	$77.90	$77.90
Purchase #3	$234.91	11.606%	$262.1737	$262.17	$262.15	$262.20
Purchase #4	$25.38	9.611%	$27.8193	$27.82	$27.80	$27.80
Purchase #5	$80.69	7.640%	$86.8547	$86.85	$86.85	$86.90
Purchase #6	$115.42	11.435%	$128.6183	$128.62	$128.60	$128.60
Purchase #7	$137.87	9.151%	$150.4865	$150.49	$150.50	$150.50
7 purchase totals =	$851.69		$938.1338	$938.13	$938.05	$938.20