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	$191.50	9.368%	$209.4397	$209.44	$209.45	$209.40
Purchase #2	$204.68	5.606%	$216.1544	$216.15	$216.15	$216.20
Purchase #3	$63.98	11.395%	$71.2705	$71.27	$71.25	$71.30
Purchase #4	$119.45	3.463%	$123.5866	$123.59	$123.60	$123.60
Purchase #5	$116.58	8.235%	$126.1804	$126.18	$126.20	$126.20
Purchase #6	$66.86	6.535%	$71.2293	$71.23	$71.25	$71.20
Purchase #7	$179.73	3.814%	$186.5849	$186.58	$186.60	$186.60
7 purchase totals =	$942.78		$1,004.4458	$1,004.44	$1,004.50	$1,004.50