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	$181.31	9.556%	$198.636	$198.64	$198.65	$198.60
Purchase #2	$128.38	3.145%	$132.4176	$132.42	$132.40	$132.40
Purchase #3	$148.90	11.806%	$166.4791	$166.48	$166.50	$166.50
Purchase #4	$233.70	6.741%	$249.4537	$249.45	$249.45	$249.50
Purchase #5	$226.55	12.498%	$254.8642	$254.86	$254.85	$254.90
Purchase #6	$92.34	12.470%	$103.8548	$103.85	$103.85	$103.90
Purchase #7	$159.51	7.537%	$171.5323	$171.53	$171.55	$171.50
7 purchase totals =	$1,170.69		$1,277.2377	$1,277.23	$1,277.25	$1,277.30