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	$47.76	12.783%	$53.8652	$53.87	$53.85	$53.90
Purchase #2	$162.56	6.332%	$172.8533	$172.85	$172.85	$172.90
Purchase #3	$221.42	7.336%	$237.6634	$237.66	$237.65	$237.70
Purchase #4	$192.54	3.457%	$199.1961	$199.20	$199.20	$199.20
Purchase #5	$75.61	8.828%	$82.2849	$82.28	$82.30	$82.30
Purchase #6	$39.72	8.572%	$43.1248	$43.12	$43.10	$43.10
Purchase #7	$230.33	8.469%	$249.8366	$249.84	$249.85	$249.80
7 purchase totals =	$969.94		$1,038.8243	$1,038.82	$1,038.80	$1,038.90