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	$209.92	9.432%	$229.7197	$229.72	$229.70	$229.70
Purchase #2	$154.99	6.228%	$164.6428	$164.64	$164.65	$164.60
Purchase #3	$19.69	3.658%	$20.4103	$20.41	$20.40	$20.40
Purchase #4	$50.67	6.294%	$53.8592	$53.86	$53.85	$53.90
Purchase #5	$69.94	5.394%	$73.7126	$73.71	$73.70	$73.70
Purchase #6	$54.82	11.769%	$61.2718	$61.27	$61.25	$61.30
Purchase #7	$20.69	4.734%	$21.6695	$21.67	$21.65	$21.70
7 purchase totals =	$580.72		$625.2859	$625.28	$625.20	$625.30