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	$127.72	9.544%	$139.9096	$139.91	$139.90	$139.90
Purchase #2	$169.80	5.669%	$179.426	$179.43	$179.45	$179.40
Purchase #3	$197.30	4.619%	$206.4133	$206.41	$206.40	$206.40
Purchase #4	$236.28	6.187%	$250.8986	$250.90	$250.90	$250.90
Purchase #5	$66.30	9.815%	$72.8073	$72.81	$72.80	$72.80
Purchase #6	$55.69	6.539%	$59.3316	$59.33	$59.35	$59.30
Purchase #7	$194.70	4.287%	$203.0468	$203.05	$203.05	$203.00
7 purchase totals =	$1,047.79		$1,111.8332	$1,111.84	$1,111.85	$1,111.70