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	$215.33	7.484%	$231.4453	$231.45	$231.45	$231.40
Purchase #2	$118.82	7.362%	$127.5675	$127.57	$127.55	$127.60
Purchase #3	$126.54	10.253%	$139.5141	$139.51	$139.50	$139.50
Purchase #4	$199.57	5.317%	$210.1811	$210.18	$210.20	$210.20
Purchase #5	$156.96	7.842%	$169.2688	$169.27	$169.25	$169.30
Purchase #6	$196.88	10.740%	$218.0249	$218.02	$218.00	$218.00
Purchase #7	$133.35	10.697%	$147.6144	$147.61	$147.60	$147.60
7 purchase totals =	$1,147.45		$1,243.6161	$1,243.61	$1,243.55	$1,243.60