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	$38.96	6.360%	$41.4379	$41.44	$41.45	$41.40
Purchase #2	$76.34	3.330%	$78.8821	$78.88	$78.90	$78.90
Purchase #3	$91.94	13.716%	$104.5505	$104.55	$104.55	$104.60
Purchase #4	$180.74	5.560%	$190.7891	$190.79	$190.80	$190.80
Purchase #5	$226.80	9.574%	$248.5138	$248.51	$248.50	$248.50
Purchase #6	$39.34	12.120%	$44.108	$44.11	$44.10	$44.10
Purchase #7	$200.57	7.211%	$215.0331	$215.03	$215.05	$215.00
7 purchase totals =	$854.69		$923.3145	$923.31	$923.35	$923.30