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	$206.48	8.124%	$223.2544	$223.25	$223.25	$223.30
Purchase #2	$97.83	11.639%	$109.2164	$109.22	$109.20	$109.20
Purchase #3	$62.69	7.795%	$67.5767	$67.58	$67.60	$67.60
Purchase #4	$25.99	6.643%	$27.7165	$27.72	$27.70	$27.70
Purchase #5	$194.70	10.668%	$215.4706	$215.47	$215.45	$215.50
Purchase #6	$160.29	3.112%	$165.2782	$165.28	$165.30	$165.30
Purchase #7	$178.92	5.362%	$188.5137	$188.51	$188.50	$188.50
7 purchase totals =	$926.90		$997.0265	$997.03	$997.00	$997.10