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	$218.32	7.572%	$234.8512	$234.85	$234.85	$234.90
Purchase #2	$209.55	8.768%	$227.9233	$227.92	$227.90	$227.90
Purchase #3	$134.75	7.406%	$144.7296	$144.73	$144.75	$144.70
Purchase #4	$145.45	6.596%	$155.0439	$155.04	$155.05	$155.00
Purchase #5	$49.79	9.747%	$54.643	$54.64	$54.65	$54.60
Purchase #6	$70.40	11.746%	$78.6692	$78.67	$78.65	$78.70
Purchase #7	$67.78	7.415%	$72.8059	$72.81	$72.80	$72.80
7 purchase totals =	$896.04		$968.6661	$968.66	$968.65	$968.60