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	$161.93	8.417%	$175.5596	$175.56	$175.55	$175.60
Purchase #2	$58.86	11.658%	$65.7219	$65.72	$65.70	$65.70
Purchase #3	$97.37	6.195%	$103.4021	$103.40	$103.40	$103.40
Purchase #4	$141.34	4.223%	$147.3088	$147.31	$147.30	$147.30
Purchase #5	$80.96	12.863%	$91.3739	$91.37	$91.35	$91.40
Purchase #6	$31.78	5.456%	$33.5139	$33.51	$33.50	$33.50
Purchase #7	$115.27	11.355%	$128.3589	$128.36	$128.35	$128.40
7 purchase totals =	$687.51		$745.2391	$745.23	$745.15	$745.30