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	$139.85	9.817%	$153.5791	$153.58	$153.60	$153.60
Purchase #2	$179.96	4.804%	$188.6053	$188.61	$188.60	$188.60
Purchase #3	$199.88	9.263%	$218.3949	$218.39	$218.40	$218.40
Purchase #4	$199.92	5.599%	$211.1135	$211.11	$211.10	$211.10
Purchase #5	$165.85	6.278%	$176.2621	$176.26	$176.25	$176.30
Purchase #6	$142.31	4.413%	$148.5901	$148.59	$148.60	$148.60
Purchase #7	$128.55	10.412%	$141.9346	$141.93	$141.95	$141.90
7 purchase totals =	$1,156.32		$1,238.4796	$1,238.47	$1,238.50	$1,238.50