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	$94.75	9.551%	$103.7996	$103.80	$103.80	$103.80
Purchase #2	$111.91	12.712%	$126.136	$126.14	$126.15	$126.10
Purchase #3	$55.76	13.166%	$63.1014	$63.10	$63.10	$63.10
Purchase #4	$77.40	6.566%	$82.4821	$82.48	$82.50	$82.50
Purchase #5	$240.76	13.418%	$273.0652	$273.07	$273.05	$273.10
Purchase #6	$180.74	12.755%	$203.7934	$203.79	$203.80	$203.80
Purchase #7	$165.32	8.317%	$179.0697	$179.07	$179.05	$179.10
7 purchase totals =	$926.64		$1,031.4474	$1,031.45	$1,031.45	$1,031.50