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	$228.45	3.307%	$236.0048	$236.00	$236.00	$236.00
Purchase #2	$179.33	11.752%	$200.4049	$200.40	$200.40	$200.40
Purchase #3	$148.32	7.772%	$159.8474	$159.85	$159.85	$159.80
Purchase #4	$54.90	11.871%	$61.4172	$61.42	$61.40	$61.40
Purchase #5	$105.60	11.711%	$117.9668	$117.97	$117.95	$118.00
Purchase #6	$203.45	6.116%	$215.893	$215.89	$215.90	$215.90
Purchase #7	$156.44	3.641%	$162.136	$162.14	$162.15	$162.10
7 purchase totals =	$1,076.49		$1,153.6701	$1,153.67	$1,153.65	$1,153.60