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	$218.58	12.570%	$246.0555	$246.06	$246.05	$246.10
Purchase #2	$49.46	10.441%	$54.6241	$54.62	$54.60	$54.60
Purchase #3	$128.29	9.661%	$140.6841	$140.68	$140.70	$140.70
Purchase #4	$92.81	8.116%	$100.3425	$100.34	$100.35	$100.30
Purchase #5	$179.83	9.317%	$196.5848	$196.58	$196.60	$196.60
Purchase #6	$243.53	7.264%	$261.22	$261.22	$261.20	$261.20
Purchase #7	$151.39	13.137%	$171.2781	$171.28	$171.30	$171.30
7 purchase totals =	$1,063.89		$1,170.7891	$1,170.78	$1,170.80	$1,170.80