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	$203.45	4.214%	$212.0234	$212.02	$212.00	$212.00
Purchase #2	$82.93	7.432%	$89.0934	$89.09	$89.10	$89.10
Purchase #3	$35.51	6.162%	$37.6981	$37.70	$37.70	$37.70
Purchase #4	$70.56	13.727%	$80.2458	$80.25	$80.25	$80.20
Purchase #5	$30.40	9.466%	$33.2777	$33.28	$33.30	$33.30
Purchase #6	$180.97	5.478%	$190.8835	$190.88	$190.90	$190.90
Purchase #7	$59.95	8.646%	$65.1333	$65.13	$65.15	$65.10
7 purchase totals =	$663.77		$708.3552	$708.35	$708.40	$708.30