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	$205.71	10.377%	$227.0565	$227.06	$227.05	$227.10
Purchase #2	$183.76	3.299%	$189.8222	$189.82	$189.80	$189.80
Purchase #3	$164.71	10.268%	$181.6224	$181.62	$181.60	$181.60
Purchase #4	$84.56	6.751%	$90.2686	$90.27	$90.25	$90.30
Purchase #5	$82.59	13.153%	$93.4531	$93.45	$93.45	$93.50
Purchase #6	$164.82	11.298%	$183.4414	$183.44	$183.45	$183.40
Purchase #7	$48.51	3.369%	$50.1443	$50.14	$50.15	$50.10
7 purchase totals =	$934.66		$1,015.8085	$1,015.80	$1,015.75	$1,015.80