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	$170.87	10.139%	$188.1945	$188.19	$188.20	$188.20
Purchase #2	$94.93	4.555%	$99.2541	$99.25	$99.25	$99.30
Purchase #3	$55.55	12.220%	$62.3382	$62.34	$62.35	$62.30
Purchase #4	$110.73	13.234%	$125.384	$125.38	$125.40	$125.40
Purchase #5	$109.87	9.508%	$120.3164	$120.32	$120.30	$120.30
Purchase #6	$178.46	7.590%	$192.0051	$192.01	$192.00	$192.00
Purchase #7	$181.44	8.496%	$196.8551	$196.86	$196.85	$196.90
7 purchase totals =	$901.85		$984.3474	$984.35	$984.35	$984.40