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	$200.97	6.556%	$214.1456	$214.15	$214.15	$214.10
Purchase #2	$225.91	6.247%	$240.0226	$240.02	$240.00	$240.00
Purchase #3	$180.30	6.230%	$191.5327	$191.53	$191.55	$191.50
Purchase #4	$70.84	11.259%	$78.8159	$78.82	$78.80	$78.80
Purchase #5	$85.31	10.441%	$94.2172	$94.22	$94.20	$94.20
Purchase #6	$201.83	10.517%	$223.0565	$223.06	$223.05	$223.10
Purchase #7	$231.41	8.156%	$250.2838	$250.28	$250.30	$250.30
7 purchase totals =	$1,196.57		$1,292.0743	$1,292.08	$1,292.05	$1,292.00