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	$137.46	10.566%	$151.984	$151.98	$152.00	$152.00
Purchase #2	$247.90	7.517%	$266.5346	$266.53	$266.55	$266.50
Purchase #3	$220.74	7.846%	$238.0593	$238.06	$238.05	$238.10
Purchase #4	$185.92	10.250%	$204.9768	$204.98	$205.00	$205.00
Purchase #5	$13.88	5.440%	$14.6351	$14.64	$14.65	$14.60
Purchase #6	$90.35	11.256%	$100.5198	$100.52	$100.50	$100.50
Purchase #7	$107.91	5.863%	$114.2368	$114.24	$114.25	$114.20
7 purchase totals =	$1,004.16		$1,090.9464	$1,090.95	$1,091.00	$1,090.90