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	$208.40	13.705%	$236.9612	$236.96	$236.95	$237.00
Purchase #2	$47.98	11.167%	$53.3379	$53.34	$53.35	$53.30
Purchase #3	$242.28	8.199%	$262.1445	$262.14	$262.15	$262.10
Purchase #4	$86.73	4.867%	$90.9511	$90.95	$90.95	$91.00
Purchase #5	$241.45	10.428%	$266.6284	$266.63	$266.65	$266.60
Purchase #6	$106.39	4.677%	$111.3659	$111.37	$111.35	$111.40
Purchase #7	$53.33	3.355%	$55.1192	$55.12	$55.10	$55.10
7 purchase totals =	$986.56		$1,076.5082	$1,076.51	$1,076.50	$1,076.50