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	$94.54	10.334%	$104.3098	$104.31	$104.30	$104.30
Purchase #2	$99.38	5.108%	$104.4563	$104.46	$104.45	$104.50
Purchase #3	$133.35	5.501%	$140.6856	$140.69	$140.70	$140.70
Purchase #4	$181.78	5.147%	$191.1362	$191.14	$191.15	$191.10
Purchase #5	$172.86	13.332%	$195.9057	$195.91	$195.90	$195.90
Purchase #6	$188.83	4.267%	$196.8874	$196.89	$196.90	$196.90
Purchase #7	$177.43	5.533%	$187.2472	$187.25	$187.25	$187.20
7 purchase totals =	$1,048.17		$1,120.6282	$1,120.65	$1,120.65	$1,120.60