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	$119.61	4.149%	$124.5726	$124.57	$124.55	$124.60
Purchase #2	$56.49	11.766%	$63.1366	$63.14	$63.15	$63.10
Purchase #3	$161.55	12.454%	$181.6694	$181.67	$181.65	$181.70
Purchase #4	$249.38	7.646%	$268.4476	$268.45	$268.45	$268.40
Purchase #5	$91.74	5.111%	$96.4288	$96.43	$96.45	$96.40
Purchase #6	$119.50	3.391%	$123.5522	$123.55	$123.55	$123.60
Purchase #7	$157.52	3.184%	$162.5354	$162.54	$162.55	$162.50
7 purchase totals =	$955.79		$1,020.3426	$1,020.35	$1,020.35	$1,020.30