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	$106.95	12.258%	$120.0599	$120.06	$120.05	$120.10
Purchase #2	$190.50	13.569%	$216.3489	$216.35	$216.35	$216.30
Purchase #3	$124.59	12.303%	$139.9183	$139.92	$139.90	$139.90
Purchase #4	$208.82	6.803%	$223.026	$223.03	$223.05	$223.00
Purchase #5	$42.36	7.132%	$45.3811	$45.38	$45.40	$45.40
Purchase #6	$98.41	4.398%	$102.7381	$102.74	$102.75	$102.70
Purchase #7	$212.32	4.658%	$222.2099	$222.21	$222.20	$222.20
7 purchase totals =	$983.95		$1,069.6822	$1,069.69	$1,069.70	$1,069.60