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	$196.43	9.661%	$215.4071	$215.41	$215.40	$215.40
Purchase #2	$113.30	6.443%	$120.5999	$120.60	$120.60	$120.60
Purchase #3	$178.43	4.306%	$186.1132	$186.11	$186.10	$186.10
Purchase #4	$242.70	12.711%	$273.5496	$273.55	$273.55	$273.50
Purchase #5	$59.39	13.210%	$67.2354	$67.24	$67.25	$67.20
Purchase #6	$110.26	7.816%	$118.8779	$118.88	$118.90	$118.90
Purchase #7	$112.39	5.543%	$118.6198	$118.62	$118.60	$118.60
7 purchase totals =	$1,012.90		$1,100.4029	$1,100.41	$1,100.40	$1,100.30