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	$173.88	7.216%	$186.4272	$186.43	$186.45	$186.40
Purchase #2	$54.92	7.431%	$59.0011	$59.00	$59.00	$59.00
Purchase #3	$125.79	11.697%	$140.5037	$140.50	$140.50	$140.50
Purchase #4	$16.74	9.870%	$18.3922	$18.39	$18.40	$18.40
Purchase #5	$182.89	12.774%	$206.2524	$206.25	$206.25	$206.30
Purchase #6	$91.81	8.287%	$99.4183	$99.42	$99.40	$99.40
Purchase #7	$213.82	8.132%	$231.2078	$231.21	$231.20	$231.20
7 purchase totals =	$859.85		$941.2027	$941.20	$941.20	$941.20