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	$169.78	5.222%	$178.6459	$178.65	$178.65	$178.60
Purchase #2	$98.56	5.373%	$103.8556	$103.86	$103.85	$103.90
Purchase #3	$60.94	3.138%	$62.8523	$62.85	$62.85	$62.90
Purchase #4	$47.30	12.787%	$53.3483	$53.35	$53.35	$53.30
Purchase #5	$57.52	7.629%	$61.9082	$61.91	$61.90	$61.90
Purchase #6	$182.51	3.685%	$189.2355	$189.24	$189.25	$189.20
Purchase #7	$90.53	5.764%	$95.7481	$95.75	$95.75	$95.70
7 purchase totals =	$707.14		$745.5939	$745.61	$745.60	$745.50