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	$164.46	4.835%	$172.4116	$172.41	$172.40	$172.40
Purchase #2	$18.42	8.702%	$20.0229	$20.02	$20.00	$20.00
Purchase #3	$240.86	6.315%	$256.0703	$256.07	$256.05	$256.10
Purchase #4	$52.72	4.848%	$55.2759	$55.28	$55.30	$55.30
Purchase #5	$124.88	11.782%	$139.5934	$139.59	$139.60	$139.60
Purchase #6	$194.68	5.322%	$205.0409	$205.04	$205.05	$205.00
Purchase #7	$202.63	8.757%	$220.3743	$220.37	$220.35	$220.40
7 purchase totals =	$998.65		$1,068.7893	$1,068.78	$1,068.75	$1,068.80