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	$151.38	3.601%	$156.8312	$156.83	$156.85	$156.80
Purchase #2	$71.25	3.509%	$73.7502	$73.75	$73.75	$73.80
Purchase #3	$74.63	10.794%	$82.6856	$82.69	$82.70	$82.70
Purchase #4	$220.59	7.613%	$237.3835	$237.38	$237.40	$237.40
Purchase #5	$68.59	7.191%	$73.5223	$73.52	$73.50	$73.50
Purchase #6	$168.81	6.792%	$180.2756	$180.28	$180.30	$180.30
Purchase #7	$182.74	11.784%	$204.2741	$204.27	$204.25	$204.30
7 purchase totals =	$937.99		$1,008.7225	$1,008.72	$1,008.75	$1,008.80