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	$38.86	9.508%	$42.5548	$42.55	$42.55	$42.60
Purchase #2	$64.92	3.223%	$67.0124	$67.01	$67.00	$67.00
Purchase #3	$144.32	12.288%	$162.054	$162.05	$162.05	$162.10
Purchase #4	$172.29	13.170%	$194.9806	$194.98	$195.00	$195.00
Purchase #5	$13.43	8.323%	$14.5478	$14.55	$14.55	$14.50
Purchase #6	$199.90	13.570%	$227.0264	$227.03	$227.05	$227.00
Purchase #7	$94.73	7.780%	$102.1	$102.10	$102.10	$102.10
7 purchase totals =	$728.45		$810.2760	$810.27	$810.30	$810.30