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	$233.91	3.398%	$241.8583	$241.86	$241.85	$241.90
Purchase #2	$155.40	4.645%	$162.6183	$162.62	$162.60	$162.60
Purchase #3	$120.75	10.681%	$133.6473	$133.65	$133.65	$133.60
Purchase #4	$7.58	3.570%	$7.8506	$7.85	$7.85	$7.90
Purchase #5	$98.75	6.765%	$105.4304	$105.43	$105.45	$105.40
Purchase #6	$220.52	7.296%	$236.6091	$236.61	$236.60	$236.60
Purchase #7	$149.72	7.472%	$160.9071	$160.91	$160.90	$160.90
7 purchase totals =	$986.63		$1,048.9211	$1,048.93	$1,048.90	$1,048.90