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	$192.61	4.263%	$200.821	$200.82	$200.80	$200.80
Purchase #2	$43.84	7.251%	$47.0188	$47.02	$47.00	$47.00
Purchase #3	$124.42	9.814%	$136.6306	$136.63	$136.65	$136.60
Purchase #4	$117.45	8.338%	$127.243	$127.24	$127.25	$127.20
Purchase #5	$148.49	5.364%	$156.455	$156.46	$156.45	$156.50
Purchase #6	$176.98	3.592%	$183.3371	$183.34	$183.35	$183.30
Purchase #7	$144.94	3.543%	$150.0752	$150.08	$150.10	$150.10
7 purchase totals =	$948.73		$1,001.5807	$1,001.59	$1,001.60	$1,001.50