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	$133.73	12.501%	$150.4476	$150.45	$150.45	$150.40
Purchase #2	$239.72	7.758%	$258.3175	$258.32	$258.30	$258.30
Purchase #3	$27.96	4.300%	$29.1623	$29.16	$29.15	$29.20
Purchase #4	$59.50	4.690%	$62.2906	$62.29	$62.30	$62.30
Purchase #5	$119.54	13.202%	$135.3217	$135.32	$135.30	$135.30
Purchase #6	$23.36	4.520%	$24.4159	$24.42	$24.40	$24.40
Purchase #7	$82.61	7.834%	$89.0817	$89.08	$89.10	$89.10
7 purchase totals =	$686.42		$749.0373	$749.04	$749.00	$749.00