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	$78.55	4.312%	$81.9371	$81.94	$81.95	$81.90
Purchase #2	$164.77	4.557%	$172.2786	$172.28	$172.30	$172.30
Purchase #3	$222.41	10.358%	$245.4472	$245.45	$245.45	$245.40
Purchase #4	$31.41	12.622%	$35.3746	$35.37	$35.35	$35.40
Purchase #5	$37.59	7.374%	$40.3619	$40.36	$40.35	$40.40
Purchase #6	$220.93	5.769%	$233.6755	$233.68	$233.70	$233.70
Purchase #7	$128.30	10.134%	$141.3019	$141.30	$141.30	$141.30
7 purchase totals =	$883.96		$950.3768	$950.38	$950.40	$950.40