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	$110.85	11.210%	$123.2763	$123.28	$123.30	$123.30
Purchase #2	$169.72	7.614%	$182.6425	$182.64	$182.65	$182.60
Purchase #3	$147.36	7.445%	$158.331	$158.33	$158.35	$158.30
Purchase #4	$190.95	10.780%	$211.5344	$211.53	$211.55	$211.50
Purchase #5	$180.38	3.646%	$186.9567	$186.96	$186.95	$187.00
Purchase #6	$103.75	13.776%	$118.0426	$118.04	$118.05	$118.00
Purchase #7	$38.75	8.550%	$42.0631	$42.06	$42.05	$42.10
7 purchase totals =	$941.76		$1,022.8466	$1,022.84	$1,022.90	$1,022.80