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	$202.43	7.811%	$218.2418	$218.24	$218.25	$218.20
Purchase #2	$35.44	8.774%	$38.5495	$38.55	$38.55	$38.50
Purchase #3	$42.53	11.640%	$47.4805	$47.48	$47.50	$47.50
Purchase #4	$135.39	11.574%	$151.06	$151.06	$151.05	$151.10
Purchase #5	$224.86	12.645%	$253.2935	$253.29	$253.30	$253.30
Purchase #6	$141.38	7.718%	$152.2917	$152.29	$152.30	$152.30
Purchase #7	$245.38	4.203%	$255.6933	$255.69	$255.70	$255.70
7 purchase totals =	$1,027.41		$1,116.6103	$1,116.60	$1,116.65	$1,116.60