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	$159.76	9.267%	$174.565	$174.57	$174.55	$174.60
Purchase #2	$161.48	12.612%	$181.8459	$181.85	$181.85	$181.80
Purchase #3	$36.40	5.188%	$38.2884	$38.29	$38.30	$38.30
Purchase #4	$203.59	3.501%	$210.7177	$210.72	$210.70	$210.70
Purchase #5	$80.30	9.358%	$87.8145	$87.81	$87.80	$87.80
Purchase #6	$164.28	5.207%	$172.8341	$172.83	$172.85	$172.80
Purchase #7	$155.78	6.135%	$165.3371	$165.34	$165.35	$165.30
7 purchase totals =	$961.59		$1,031.4027	$1,031.41	$1,031.40	$1,031.30