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	$34.54	7.539%	$37.144	$37.14	$37.15	$37.10
Purchase #2	$83.73	11.698%	$93.5247	$93.52	$93.50	$93.50
Purchase #3	$104.64	8.552%	$113.5888	$113.59	$113.60	$113.60
Purchase #4	$70.39	6.628%	$75.0554	$75.06	$75.05	$75.10
Purchase #5	$129.76	8.801%	$141.1802	$141.18	$141.20	$141.20
Purchase #6	$211.52	11.826%	$236.5344	$236.53	$236.55	$236.50
Purchase #7	$131.32	8.448%	$142.4139	$142.41	$142.40	$142.40
7 purchase totals =	$765.90		$839.4414	$839.43	$839.45	$839.40