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	$159.34	11.304%	$177.3518	$177.35	$177.35	$177.40
Purchase #2	$238.58	9.628%	$261.5505	$261.55	$261.55	$261.60
Purchase #3	$11.34	9.801%	$12.4514	$12.45	$12.45	$12.50
Purchase #4	$128.27	12.847%	$144.7488	$144.75	$144.75	$144.70
Purchase #5	$152.63	10.516%	$168.6806	$168.68	$168.70	$168.70
Purchase #6	$172.46	13.836%	$196.3216	$196.32	$196.30	$196.30
Purchase #7	$51.64	10.829%	$57.2321	$57.23	$57.25	$57.20
7 purchase totals =	$914.26		$1,018.3368	$1,018.33	$1,018.35	$1,018.40