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	$24.66	9.672%	$27.0451	$27.05	$27.05	$27.00
Purchase #2	$233.94	3.606%	$242.3759	$242.38	$242.40	$242.40
Purchase #3	$224.48	10.449%	$247.9359	$247.94	$247.95	$247.90
Purchase #4	$155.98	5.865%	$165.1282	$165.13	$165.15	$165.10
Purchase #5	$73.34	6.507%	$78.1122	$78.11	$78.10	$78.10
Purchase #6	$28.55	10.260%	$31.4792	$31.48	$31.50	$31.50
Purchase #7	$220.32	11.227%	$245.0553	$245.06	$245.05	$245.10
7 purchase totals =	$961.27		$1,037.1318	$1,037.15	$1,037.20	$1,037.10