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	$133.81	6.143%	$142.0299	$142.03	$142.05	$142.00
Purchase #2	$125.68	10.838%	$139.3012	$139.30	$139.30	$139.30
Purchase #3	$140.47	8.757%	$152.771	$152.77	$152.75	$152.80
Purchase #4	$107.77	8.567%	$117.0027	$117.00	$117.00	$117.00
Purchase #5	$242.86	11.388%	$270.5169	$270.52	$270.50	$270.50
Purchase #6	$100.89	10.286%	$111.2675	$111.27	$111.25	$111.30
Purchase #7	$179.36	8.618%	$194.8172	$194.82	$194.80	$194.80
7 purchase totals =	$1,030.84		$1,127.7064	$1,127.71	$1,127.65	$1,127.70