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	$137.92	10.263%	$152.0747	$152.07	$152.05	$152.10
Purchase #2	$33.52	11.830%	$37.4854	$37.49	$37.50	$37.50
Purchase #3	$93.55	5.121%	$98.3407	$98.34	$98.35	$98.30
Purchase #4	$107.70	6.438%	$114.6337	$114.63	$114.65	$114.60
Purchase #5	$151.65	11.396%	$168.932	$168.93	$168.95	$168.90
Purchase #6	$62.46	12.247%	$70.1095	$70.11	$70.10	$70.10
Purchase #7	$73.54	7.158%	$78.804	$78.80	$78.80	$78.80
7 purchase totals =	$660.34		$720.3800	$720.37	$720.40	$720.30