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	$249.96	9.596%	$273.9462	$273.95	$273.95	$273.90
Purchase #2	$67.68	5.165%	$71.1757	$71.18	$71.20	$71.20
Purchase #3	$46.29	4.573%	$48.4068	$48.41	$48.40	$48.40
Purchase #4	$38.41	8.304%	$41.5996	$41.60	$41.60	$41.60
Purchase #5	$212.47	4.632%	$222.3116	$222.31	$222.30	$222.30
Purchase #6	$155.56	10.662%	$172.1458	$172.15	$172.15	$172.10
Purchase #7	$187.75	6.441%	$199.843	$199.84	$199.85	$199.80
7 purchase totals =	$958.12		$1,029.4287	$1,029.44	$1,029.45	$1,029.30