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	$20.77	8.821%	$22.6021	$22.60	$22.60	$22.60
Purchase #2	$144.25	7.396%	$154.9187	$154.92	$154.90	$154.90
Purchase #3	$226.31	4.575%	$236.6637	$236.66	$236.65	$236.70
Purchase #4	$62.59	7.261%	$67.1347	$67.13	$67.15	$67.10
Purchase #5	$79.61	4.866%	$83.4838	$83.48	$83.50	$83.50
Purchase #6	$244.31	4.178%	$254.5173	$254.52	$254.50	$254.50
Purchase #7	$234.46	3.782%	$243.3273	$243.33	$243.35	$243.30
7 purchase totals =	$1,012.30		$1,062.6476	$1,062.64	$1,062.65	$1,062.60