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	$151.96	9.829%	$166.8961	$166.90	$166.90	$166.90
Purchase #2	$144.54	11.217%	$160.7531	$160.75	$160.75	$160.80
Purchase #3	$132.42	8.597%	$143.8041	$143.80	$143.80	$143.80
Purchase #4	$39.96	8.746%	$43.4549	$43.45	$43.45	$43.50
Purchase #5	$98.53	13.816%	$112.1429	$112.14	$112.15	$112.10
Purchase #6	$234.54	4.626%	$245.3898	$245.39	$245.40	$245.40
Purchase #7	$120.38	10.494%	$133.0127	$133.01	$133.00	$133.00
7 purchase totals =	$922.33		$1,005.4536	$1,005.44	$1,005.45	$1,005.50