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	$227.94	11.303%	$253.7041	$253.70	$253.70	$253.70
Purchase #2	$199.30	12.483%	$224.1786	$224.18	$224.20	$224.20
Purchase #3	$226.53	11.196%	$251.8923	$251.89	$251.90	$251.90
Purchase #4	$235.50	6.540%	$250.9017	$250.90	$250.90	$250.90
Purchase #5	$43.83	3.394%	$45.3176	$45.32	$45.30	$45.30
Purchase #6	$100.50	10.872%	$111.4264	$111.43	$111.45	$111.40
Purchase #7	$75.33	7.765%	$81.1794	$81.18	$81.20	$81.20
7 purchase totals =	$1,108.93		$1,218.6001	$1,218.60	$1,218.65	$1,218.60