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	$32.43	4.589%	$33.9182	$33.92	$33.90	$33.90
Purchase #2	$73.27	10.598%	$81.0352	$81.04	$81.05	$81.00
Purchase #3	$95.46	4.275%	$99.5409	$99.54	$99.55	$99.50
Purchase #4	$170.64	4.328%	$178.0253	$178.03	$178.05	$178.00
Purchase #5	$89.26	6.223%	$94.8146	$94.81	$94.80	$94.80
Purchase #6	$182.34	5.465%	$192.3049	$192.30	$192.30	$192.30
Purchase #7	$80.27	7.615%	$86.3826	$86.38	$86.40	$86.40
7 purchase totals =	$723.67		$766.0217	$766.02	$766.05	$765.90