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	$218.34	11.363%	$243.15	$243.15	$243.15	$243.20
Purchase #2	$206.97	4.860%	$217.0287	$217.03	$217.05	$217.00
Purchase #3	$183.67	9.408%	$200.9497	$200.95	$200.95	$200.90
Purchase #4	$75.72	12.589%	$85.2524	$85.25	$85.25	$85.30
Purchase #5	$132.80	4.131%	$138.286	$138.29	$138.30	$138.30
Purchase #6	$56.95	4.706%	$59.6301	$59.63	$59.65	$59.60
Purchase #7	$56.72	7.127%	$60.7624	$60.76	$60.75	$60.80
7 purchase totals =	$931.17		$1,005.0593	$1,005.06	$1,005.10	$1,005.10